diff --git a/apps/ca.c b/apps/ca.c
index 454c218..23c7f05 100644
--- a/apps/ca.c
+++ b/apps/ca.c
@@ -2379,7 +2379,7 @@
 
     case REV_CRL_REASON:
         for (i = 0; i < 8; i++) {
-            if (strcasecmp(rev_arg, crl_reasons[i]) == 0) {
+            if (OPENSSL_strcasecmp(rev_arg, crl_reasons[i]) == 0) {
                 reason = crl_reasons[i];
                 break;
             }
@@ -2596,7 +2596,7 @@
     }
     if (reason_str) {
         for (i = 0; i < NUM_REASONS; i++) {
-            if (strcasecmp(reason_str, crl_reasons[i]) == 0) {
+            if (OPENSSL_strcasecmp(reason_str, crl_reasons[i]) == 0) {
                 reason_code = i;
                 break;
             }
diff --git a/apps/ecparam.c b/apps/ecparam.c
index 9910d8c..4fdae06 100644
--- a/apps/ecparam.c
+++ b/apps/ecparam.c
@@ -228,7 +228,7 @@
                        point_format, 0);
         *p = OSSL_PARAM_construct_end();
 
-        if (strcasecmp(curve_name, "SM2") == 0)
+        if (OPENSSL_strcasecmp(curve_name, "SM2") == 0)
             gctx_params = EVP_PKEY_CTX_new_from_name(NULL, "sm2", NULL);
         else
             gctx_params = EVP_PKEY_CTX_new_from_name(NULL, "ec", NULL);
diff --git a/apps/lib/apps.c b/apps/lib/apps.c
index e3afc57..317a000 100644
--- a/apps/lib/apps.c
+++ b/apps/lib/apps.c
@@ -1145,20 +1145,20 @@
 
 int set_dateopt(unsigned long *dateopt, const char *arg)
 {
-    if (strcasecmp(arg, "rfc_822") == 0)
+    if (OPENSSL_strcasecmp(arg, "rfc_822") == 0)
         *dateopt = ASN1_DTFLGS_RFC822;
-    else if (strcasecmp(arg, "iso_8601") == 0)
+    else if (OPENSSL_strcasecmp(arg, "iso_8601") == 0)
         *dateopt = ASN1_DTFLGS_ISO8601;
     return 0;
 }
 
 int set_ext_copy(int *copy_type, const char *arg)
 {
-    if (strcasecmp(arg, "none") == 0)
+    if (OPENSSL_strcasecmp(arg, "none") == 0)
         *copy_type = EXT_COPY_NONE;
-    else if (strcasecmp(arg, "copy") == 0)
+    else if (OPENSSL_strcasecmp(arg, "copy") == 0)
         *copy_type = EXT_COPY_ADD;
-    else if (strcasecmp(arg, "copyall") == 0)
+    else if (OPENSSL_strcasecmp(arg, "copyall") == 0)
         *copy_type = EXT_COPY_ALL;
     else
         return 0;
@@ -1239,7 +1239,7 @@
     }
 
     for (ptbl = in_tbl; ptbl->name; ptbl++) {
-        if (strcasecmp(arg, ptbl->name) == 0) {
+        if (OPENSSL_strcasecmp(arg, ptbl->name) == 0) {
             *flags &= ~ptbl->mask;
             if (c)
                 *flags |= ptbl->flag;
diff --git a/apps/lib/http_server.c b/apps/lib/http_server.c
index e531201..36ea7a3 100644
--- a/apps/lib/http_server.c
+++ b/apps/lib/http_server.c
@@ -468,10 +468,11 @@
         }
         *line_end = '\0';
         /* https://tools.ietf.org/html/rfc7230#section-6.3 Persistence */
-        if (found_keep_alive != NULL && strcasecmp(key, "Connection") == 0) {
-            if (strcasecmp(value, "keep-alive") == 0)
+        if (found_keep_alive != NULL
+            && OPENSSL_strcasecmp(key, "Connection") == 0) {
+            if (OPENSSL_strcasecmp(value, "keep-alive") == 0)
                 *found_keep_alive = 1;
-            else if (strcasecmp(value, "close") == 0)
+            else if (OPENSSL_strcasecmp(value, "close") == 0)
                 *found_keep_alive = 0;
         }
     }
diff --git a/apps/lib/names.c b/apps/lib/names.c
index 5e2e7e1..d42de5a 100644
--- a/apps/lib/names.c
+++ b/apps/lib/names.c
@@ -11,14 +11,11 @@
 #include <openssl/bio.h>
 #include <openssl/safestack.h>
 #include "names.h"
-
-#ifdef _WIN32
-# define strcasecmp _stricmp
-#endif
+#include "internal/e_os.h"
 
 int name_cmp(const char * const *a, const char * const *b)
 {
-    return strcasecmp(*a, *b);
+    return OPENSSL_strcasecmp(*a, *b);
 }
 
 void collect_names(const char *name, void *vdata)
diff --git a/apps/lib/vms_term_sock.c b/apps/lib/vms_term_sock.c
index a1aeb6d..e4bf0f6 100644
--- a/apps/lib/vms_term_sock.c
+++ b/apps/lib/vms_term_sock.c
@@ -132,7 +132,7 @@
         len;
 
     LogMessage ("Enter 'q' or 'Q' to quit ...");
-    while (strcasecmp (TermBuff, "Q")) {
+    while (OPENSSL_strcasecmp (TermBuff, "Q")) {
         /*
         ** Create the terminal socket
         */
diff --git a/apps/list.c b/apps/list.c
index 30bf2be..c6ff7dd 100644
--- a/apps/list.c
+++ b/apps/list.c
@@ -71,7 +71,7 @@
 {
     if (select_name != NULL
         && (c == NULL
-            || strcasecmp(select_name,  EVP_CIPHER_get0_name(c)) != 0))
+            || OPENSSL_strcasecmp(select_name,  EVP_CIPHER_get0_name(c)) != 0))
         return;
     if (c != NULL) {
         BIO_printf(arg, "  %s\n", EVP_CIPHER_get0_name(c));
@@ -370,7 +370,7 @@
 
 static int rand_cmp(const EVP_RAND * const *a, const EVP_RAND * const *b)
 {
-    int ret = strcasecmp(EVP_RAND_get0_name(*a), EVP_RAND_get0_name(*b));
+    int ret = OPENSSL_strcasecmp(EVP_RAND_get0_name(*a), EVP_RAND_get0_name(*b));
 
     if (ret == 0)
         ret = strcmp(OSSL_PROVIDER_get0_name(EVP_RAND_get0_provider(*a)),
@@ -404,7 +404,7 @@
         const EVP_RAND *m = sk_EVP_RAND_value(rands, i);
 
         if (select_name != NULL
-            && strcasecmp(EVP_RAND_get0_name(m), select_name) != 0)
+            && OPENSSL_strcasecmp(EVP_RAND_get0_name(m), select_name) != 0)
             continue;
         BIO_printf(bio_out, "  %s", EVP_RAND_get0_name(m));
         BIO_printf(bio_out, " @ %s\n",
@@ -463,7 +463,7 @@
         if (gettables != NULL)
             for (; gettables->key != NULL; gettables++) {
                 /* State has been dealt with already, so ignore */
-                if (strcasecmp(gettables->key, OSSL_RAND_PARAM_STATE) == 0)
+                if (OPENSSL_strcasecmp(gettables->key, OSSL_RAND_PARAM_STATE) == 0)
                     continue;
                 /* Outside of verbose mode, we skip non-string values */
                 if (gettables->data_type != OSSL_PARAM_UTF8_STRING
diff --git a/apps/rehash.c b/apps/rehash.c
index e0b7954..eb538bf 100644
--- a/apps/rehash.c
+++ b/apps/rehash.c
@@ -213,9 +213,10 @@
     if (filename[i++] != '.')
         return -1;
     for (type = OSSL_NELEM(suffixes) - 1; type > 0; type--)
-        if (strncasecmp(&filename[i],
-                        suffixes[type], strlen(suffixes[type])) == 0)
+        if (OPENSSL_strncasecmp(&filename[i],
+                                suffixes[type], strlen(suffixes[type])) == 0)
             break;
+
     i += strlen(suffixes[type]);
 
     id = strtoul(&filename[i], &endptr, 10);
@@ -248,7 +249,7 @@
     if ((ext = strrchr(filename, '.')) == NULL)
         goto end;
     for (i = 0; i < OSSL_NELEM(extensions); i++) {
-        if (strcasecmp(extensions[i], ext + 1) == 0)
+        if (OPENSSL_strcasecmp(extensions[i], ext + 1) == 0)
             break;
     }
     if (i >= OSSL_NELEM(extensions))
diff --git a/apps/s_server.c b/apps/s_server.c
index 736d849..cdcec47 100644
--- a/apps/s_server.c
+++ b/apps/s_server.c
@@ -432,7 +432,7 @@
         return SSL_TLSEXT_ERR_NOACK;
 
     if (servername != NULL) {
-        if (strcasecmp(servername, p->servername))
+        if (OPENSSL_strcasecmp(servername, p->servername))
             return p->extension_error;
         if (ctx2 != NULL) {
             BIO_printf(p->biodebug, "Switching server context.\n");
diff --git a/crypto/LPdir_unix.c b/crypto/LPdir_unix.c
index 4151d1b..38f5356 100644
--- a/crypto/LPdir_unix.c
+++ b/crypto/LPdir_unix.c
@@ -141,7 +141,8 @@
             p--;
         if (p > (*ctx)->entry_name && p[-1] == ';')
             p[-1] = '\0';
-        if (strcasecmp((*ctx)->entry_name, (*ctx)->previous_entry_name) == 0)
+        if (OPENSSL_strcasecmp((*ctx)->entry_name,
+                               (*ctx)->previous_entry_name) == 0)
             goto again;
     }
 #endif
diff --git a/crypto/asn1/ameth_lib.c b/crypto/asn1/ameth_lib.c
index 9704492..0de5785 100644
--- a/crypto/asn1/ameth_lib.c
+++ b/crypto/asn1/ameth_lib.c
@@ -10,7 +10,6 @@
 /* We need to use some engine deprecated APIs */
 #define OPENSSL_SUPPRESS_DEPRECATED
 
-#include "internal/e_os.h"               /* for strncasecmp */
 #include "internal/cryptlib.h"
 #include <stdio.h>
 #include <openssl/asn1t.h>
@@ -134,7 +133,7 @@
         if (ameth->pkey_flags & ASN1_PKEY_ALIAS)
             continue;
         if ((int)strlen(ameth->pem_str) == len
-            && strncasecmp(ameth->pem_str, str, len) == 0)
+            && OPENSSL_strncasecmp(ameth->pem_str, str, len) == 0)
             return ameth;
     }
     return NULL;
diff --git a/crypto/asn1/asn1_gen.c b/crypto/asn1/asn1_gen.c
index a112f7d..ef5b701 100644
--- a/crypto/asn1/asn1_gen.c
+++ b/crypto/asn1/asn1_gen.c
@@ -10,7 +10,6 @@
 #include "internal/cryptlib.h"
 #include <openssl/asn1.h>
 #include <openssl/x509v3.h>
-#include "internal/e_os.h" /* strncasecmp() */
 
 #define ASN1_GEN_FLAG           0x10000
 #define ASN1_GEN_FLAG_IMP       (ASN1_GEN_FLAG|1)
@@ -565,7 +564,8 @@
 
     tntmp = tnst;
     for (i = 0; i < OSSL_NELEM(tnst); i++, tntmp++) {
-        if ((len == tntmp->len) && (strncasecmp(tntmp->strnam, tagstr, len) == 0))
+        if ((len == tntmp->len)
+            && (OPENSSL_strncasecmp(tntmp->strnam, tagstr, len) == 0))
             return tntmp->tag;
     }
 
diff --git a/crypto/conf/conf_def.c b/crypto/conf/conf_def.c
index 9d79a90..ef45e7d 100644
--- a/crypto/conf/conf_def.c
+++ b/crypto/conf/conf_def.c
@@ -11,7 +11,7 @@
 
 #include <stdio.h>
 #include <string.h>
-#include "internal/e_os.h" /* strcasecmp and struct stat */
+#include "internal/e_os.h" /* struct stat */
 #ifdef __TANDEM
 # include <sys/types.h> /* needed for stat.h */
 # include <sys/stat.h> /* struct stat */
@@ -192,11 +192,11 @@
 /* Parse a boolean value and fill in *flag. Return 0 on error. */
 static int parsebool(const char *pval, int *flag)
 {
-    if (strcasecmp(pval, "on") == 0
-            || strcasecmp(pval, "true") == 0) {
+    if (OPENSSL_strcasecmp(pval, "on") == 0
+        || OPENSSL_strcasecmp(pval, "true") == 0) {
         *flag = 1;
-    } else if (strcasecmp(pval, "off") == 0
-            || strcasecmp(pval, "false") == 0) {
+    } else if (OPENSSL_strcasecmp(pval, "off") == 0
+               || OPENSSL_strcasecmp(pval, "false") == 0) {
         *flag = 0;
     } else {
         ERR_raise(ERR_LIB_CONF, CONF_R_INVALID_PRAGMA);
@@ -839,8 +839,10 @@
         namelen = strlen(filename);
 
 
-        if ((namelen > 5 && strcasecmp(filename + namelen - 5, ".conf") == 0)
-            || (namelen > 4 && strcasecmp(filename + namelen - 4, ".cnf") == 0)) {
+        if ((namelen > 5
+             && OPENSSL_strcasecmp(filename + namelen - 5, ".conf") == 0)
+            || (namelen > 4
+                && OPENSSL_strcasecmp(filename + namelen - 4, ".cnf") == 0)) {
             size_t newlen;
             char *newpath;
             BIO *bio;
diff --git a/crypto/core_namemap.c b/crypto/core_namemap.c
index d8de0af..e4be318 100644
--- a/crypto/core_namemap.c
+++ b/crypto/core_namemap.c
@@ -7,7 +7,6 @@
  * https://www.openssl.org/source/license.html
  */
 
-#include "internal/e_os.h"                /* strcasecmp */
 #include "internal/namemap.h"
 #include <openssl/lhash.h>
 #include "crypto/lhash.h"      /* ossl_lh_strcasehash */
@@ -50,7 +49,7 @@
 
 static int namenum_cmp(const NAMENUM_ENTRY *a, const NAMENUM_ENTRY *b)
 {
-    return strcasecmp(a->name, b->name);
+    return OPENSSL_strcasecmp(a->name, b->name);
 }
 
 static void namenum_free(NAMENUM_ENTRY *n)
diff --git a/crypto/dh/dh_group_params.c b/crypto/dh/dh_group_params.c
index dec50ca..7608cba 100644
--- a/crypto/dh/dh_group_params.c
+++ b/crypto/dh/dh_group_params.c
@@ -23,7 +23,6 @@
 #include <openssl/objects.h>
 #include "internal/nelem.h"
 #include "crypto/dh.h"
-#include "internal/e_os.h" /* strcasecmp */
 
 static DH *dh_param_init(OSSL_LIB_CTX *libctx, const DH_NAMED_GROUP *group)
 {
diff --git a/crypto/ec/ec_backend.c b/crypto/ec/ec_backend.c
index d2fff06..935e5cf 100644
--- a/crypto/ec/ec_backend.c
+++ b/crypto/ec/ec_backend.c
@@ -54,7 +54,7 @@
         return OPENSSL_EC_NAMED_CURVE;
 
     for (i = 0, sz = OSSL_NELEM(encoding_nameid_map); i < sz; i++) {
-        if (strcasecmp(name, encoding_nameid_map[i].ptr) == 0)
+        if (OPENSSL_strcasecmp(name, encoding_nameid_map[i].ptr) == 0)
             return encoding_nameid_map[i].id;
     }
     return -1;
@@ -91,7 +91,7 @@
         return 0;
 
     for (i = 0, sz = OSSL_NELEM(check_group_type_nameid_map); i < sz; i++) {
-        if (strcasecmp(name, check_group_type_nameid_map[i].ptr) == 0)
+        if (OPENSSL_strcasecmp(name, check_group_type_nameid_map[i].ptr) == 0)
             return check_group_type_nameid_map[i].id;
     }
     return -1;
@@ -136,7 +136,7 @@
         return (int)POINT_CONVERSION_UNCOMPRESSED;
 
     for (i = 0, sz = OSSL_NELEM(format_nameid_map); i < sz; i++) {
-        if (strcasecmp(name, format_nameid_map[i].ptr) == 0)
+        if (OPENSSL_strcasecmp(name, format_nameid_map[i].ptr) == 0)
             return format_nameid_map[i].id;
     }
     return -1;
diff --git a/crypto/ec/ec_lib.c b/crypto/ec/ec_lib.c
index f686e45..f22ba67 100644
--- a/crypto/ec/ec_lib.c
+++ b/crypto/ec/ec_lib.c
@@ -22,7 +22,6 @@
 #include "crypto/ec.h"
 #include "internal/nelem.h"
 #include "ec_local.h"
-#include "internal/e_os.h" /* strcasecmp */
 
 /* functions for EC_GROUP objects */
 
@@ -1592,9 +1591,10 @@
         ERR_raise(ERR_LIB_EC, EC_R_INVALID_FIELD);
         goto err;
     }
-    if (strcasecmp(ptmp->data, SN_X9_62_prime_field) == 0) {
+    if (OPENSSL_strcasecmp(ptmp->data, SN_X9_62_prime_field) == 0) {
         is_prime_field = 1;
-    } else if (strcasecmp(ptmp->data, SN_X9_62_characteristic_two_field) == 0) {
+    } else if (OPENSSL_strcasecmp(ptmp->data,
+                                  SN_X9_62_characteristic_two_field) == 0) {
         is_prime_field = 0;
     } else {
         /* Invalid field */
diff --git a/crypto/encode_decode/decoder_lib.c b/crypto/encode_decode/decoder_lib.c
index 6781c61..768c58c 100644
--- a/crypto/encode_decode/decoder_lib.c
+++ b/crypto/encode_decode/decoder_lib.c
@@ -796,7 +796,7 @@
          */
         trace_data_structure = data_structure;
         if (data_type != NULL && data_structure != NULL
-            && strcasecmp(data_structure, "type-specific") == 0)
+            && OPENSSL_strcasecmp(data_structure, "type-specific") == 0)
             data_structure = NULL;
 
         OSSL_TRACE_BEGIN(DECODER) {
@@ -857,7 +857,7 @@
          * that's the case, we do this extra check.
          */
         if (decoder == NULL && ctx->start_input_type != NULL
-            && strcasecmp(ctx->start_input_type, new_input_type) != 0) {
+            && OPENSSL_strcasecmp(ctx->start_input_type, new_input_type) != 0) {
             OSSL_TRACE_BEGIN(DECODER) {
                 BIO_printf(trc_out,
                            "(ctx %p) %s [%u] the start input type '%s' doesn't match the input type of the considered decoder, skipping...\n",
@@ -904,7 +904,8 @@
          */
         if (data_structure != NULL
             && (new_input_structure == NULL
-                || strcasecmp(data_structure, new_input_structure) != 0)) {
+                || OPENSSL_strcasecmp(data_structure,
+                                      new_input_structure) != 0)) {
             OSSL_TRACE_BEGIN(DECODER) {
                 BIO_printf(trc_out,
                            "(ctx %p) %s [%u] the previous decoder's data structure doesn't match the input structure of the considered decoder, skipping...\n",
@@ -923,7 +924,8 @@
             && ctx->input_structure != NULL
             && new_input_structure != NULL) {
             data->flag_input_structure_checked = 1;
-            if (strcasecmp(new_input_structure, ctx->input_structure) != 0) {
+            if (OPENSSL_strcasecmp(new_input_structure,
+                                   ctx->input_structure) != 0) {
                 OSSL_TRACE_BEGIN(DECODER) {
                     BIO_printf(trc_out,
                                "(ctx %p) %s [%u] the previous decoder's data structure doesn't match the input structure given by the user, skipping...\n",
diff --git a/crypto/encode_decode/decoder_pkey.c b/crypto/encode_decode/decoder_pkey.c
index 8cb320a..268c05c 100644
--- a/crypto/encode_decode/decoder_pkey.c
+++ b/crypto/encode_decode/decoder_pkey.c
@@ -19,7 +19,6 @@
 #include "crypto/decoder.h"
 #include "crypto/evp/evp_local.h"
 #include "encoder_local.h"
-#include "internal/e_os.h"                /* strcasecmp on Windows */
 #include "internal/namemap.h"
 
 int OSSL_DECODER_CTX_set_passphrase(OSSL_DECODER_CTX *ctx,
diff --git a/crypto/encode_decode/encoder_lib.c b/crypto/encode_decode/encoder_lib.c
index 52cc404..ded8bae 100644
--- a/crypto/encode_decode/encoder_lib.c
+++ b/crypto/encode_decode/encoder_lib.c
@@ -7,7 +7,6 @@
  * https://www.openssl.org/source/license.html
  */
 
-#include "internal/e_os.h"                /* strcasecmp on Windows */
 #include <openssl/core_names.h>
 #include <openssl/bio.h>
 #include <openssl/encoder.h>
@@ -453,8 +452,8 @@
          */
         if (top) {
             if (data->ctx->output_type != NULL
-                && strcasecmp(current_output_type,
-                              data->ctx->output_type) != 0) {
+                && OPENSSL_strcasecmp(current_output_type,
+                                      data->ctx->output_type) != 0) {
                 OSSL_TRACE_BEGIN(ENCODER) {
                     BIO_printf(trc_out,
                                "[%d]    Skipping because current encoder output type (%s) != desired output type (%s)\n",
@@ -482,8 +481,8 @@
          */
         if (data->ctx->output_structure != NULL
             && current_output_structure != NULL) {
-            if (strcasecmp(data->ctx->output_structure,
-                           current_output_structure) != 0) {
+            if (OPENSSL_strcasecmp(data->ctx->output_structure,
+                                   current_output_structure) != 0) {
                 OSSL_TRACE_BEGIN(ENCODER) {
                     BIO_printf(trc_out,
                                "[%d]    Skipping because current encoder output structure (%s) != ctx output structure (%s)\n",
diff --git a/crypto/encode_decode/encoder_pkey.c b/crypto/encode_decode/encoder_pkey.c
index 74765a5..e39ec27 100644
--- a/crypto/encode_decode/encoder_pkey.c
+++ b/crypto/encode_decode/encoder_pkey.c
@@ -7,7 +7,6 @@
  * https://www.openssl.org/source/license.html
  */
 
-#include "internal/e_os.h"                /* strcasecmp on Windows */
 #include <openssl/err.h>
 #include <openssl/ui.h>
 #include <openssl/params.h>
diff --git a/crypto/engine/tb_asnmth.c b/crypto/engine/tb_asnmth.c
index bf424ff..3d0fdc5 100644
--- a/crypto/engine/tb_asnmth.c
+++ b/crypto/engine/tb_asnmth.c
@@ -152,7 +152,7 @@
         e->pkey_asn1_meths(e, &ameth, NULL, nids[i]);
         if (ameth != NULL
             && ((int)strlen(ameth->pem_str) == len)
-            && strncasecmp(ameth->pem_str, str, len) == 0)
+            && OPENSSL_strncasecmp(ameth->pem_str, str, len) == 0)
             return ameth;
     }
     return NULL;
@@ -177,7 +177,7 @@
         e->pkey_asn1_meths(e, &ameth, NULL, nid);
         if (ameth != NULL
                 && ((int)strlen(ameth->pem_str) == lk->len)
-                && strncasecmp(ameth->pem_str, lk->str, lk->len) == 0) {
+                && OPENSSL_strncasecmp(ameth->pem_str, lk->str, lk->len) == 0) {
             lk->e = e;
             lk->ameth = ameth;
             return;
diff --git a/crypto/evp/ctrl_params_translate.c b/crypto/evp/ctrl_params_translate.c
index 33e5e7f..74df2fd 100644
--- a/crypto/evp/ctrl_params_translate.c
+++ b/crypto/evp/ctrl_params_translate.c
@@ -37,8 +37,6 @@
 #include "crypto/dh.h"
 #include "crypto/ec.h"
 
-#include "internal/e_os.h"                /* strcasecmp() for Windows */
-
 struct translation_ctx_st;       /* Forwarding */
 struct translation_st;           /* Forwarding */
 
@@ -905,7 +903,7 @@
 
         /* Convert KDF type strings to numbers */
         for (; kdf_type_map->kdf_type_str != NULL; kdf_type_map++)
-            if (strcasecmp(ctx->p2, kdf_type_map->kdf_type_str) == 0) {
+            if (OPENSSL_strcasecmp(ctx->p2, kdf_type_map->kdf_type_str) == 0) {
                 ctx->p1 = kdf_type_map->kdf_type_num;
                 ret = 1;
                 break;
@@ -2469,10 +2467,11 @@
              * cmd name in the template.
              */
             if (item->ctrl_str != NULL
-                && strcasecmp(tmpl->ctrl_str, item->ctrl_str) == 0)
+                && OPENSSL_strcasecmp(tmpl->ctrl_str, item->ctrl_str) == 0)
                 ctrl_str = tmpl->ctrl_str;
             else if (item->ctrl_hexstr != NULL
-                     && strcasecmp(tmpl->ctrl_hexstr, item->ctrl_hexstr) == 0)
+                     && OPENSSL_strcasecmp(tmpl->ctrl_hexstr,
+                                           item->ctrl_hexstr) == 0)
                 ctrl_hexstr = tmpl->ctrl_hexstr;
             else
                 continue;
@@ -2500,7 +2499,8 @@
             if ((item->action_type != NONE
                  && tmpl->action_type != item->action_type)
                 || (item->param_key != NULL
-                    && strcasecmp(tmpl->param_key, item->param_key) != 0))
+                    && OPENSSL_strcasecmp(tmpl->param_key,
+                                          item->param_key) != 0))
                 continue;
         } else {
             return NULL;
diff --git a/crypto/evp/ec_support.c b/crypto/evp/ec_support.c
index 979e861..aa3c7fa 100644
--- a/crypto/evp/ec_support.c
+++ b/crypto/evp/ec_support.c
@@ -10,7 +10,7 @@
 #include <string.h>
 #include <openssl/ec.h>
 #include "crypto/ec.h"
-#include "internal/e_os.h" /* strcasecmp required by windows */
+#include "internal/nelem.h"
 
 typedef struct ec_name2nid_st {
     const char *name;
@@ -139,7 +139,7 @@
             return nid;
 
         for (i = 0; i < OSSL_NELEM(curve_list); i++) {
-            if (strcasecmp(curve_list[i].name, name) == 0)
+            if (OPENSSL_strcasecmp(curve_list[i].name, name) == 0)
                 return curve_list[i].nid;
         }
     }
diff --git a/crypto/evp/evp_lib.c b/crypto/evp/evp_lib.c
index 7e03d03..85a3c4f 100644
--- a/crypto/evp/evp_lib.c
+++ b/crypto/evp/evp_lib.c
@@ -15,7 +15,6 @@
 
 #include <stdio.h>
 #include <string.h>
-#include "internal/e_os.h" /* strcasecmp */
 #include "internal/cryptlib.h"
 #include <openssl/evp.h>
 #include <openssl/objects.h>
@@ -1194,17 +1193,17 @@
 
     va_start(args, type);
 
-    if (strcasecmp(type, "RSA") == 0) {
+    if (OPENSSL_strcasecmp(type, "RSA") == 0) {
         bits = va_arg(args, size_t);
         params[0] = OSSL_PARAM_construct_size_t(OSSL_PKEY_PARAM_RSA_BITS, &bits);
-    } else if (strcasecmp(type, "EC") == 0) {
+    } else if (OPENSSL_strcasecmp(type, "EC") == 0) {
         name = va_arg(args, char *);
         params[0] = OSSL_PARAM_construct_utf8_string(OSSL_PKEY_PARAM_GROUP_NAME,
                                                      name, 0);
-    } else if (strcasecmp(type, "ED25519") != 0
-               && strcasecmp(type, "X25519") != 0
-               && strcasecmp(type, "ED448") != 0
-               && strcasecmp(type, "X448") != 0) {
+    } else if (OPENSSL_strcasecmp(type, "ED25519") != 0
+               && OPENSSL_strcasecmp(type, "X25519") != 0
+               && OPENSSL_strcasecmp(type, "ED448") != 0
+               && OPENSSL_strcasecmp(type, "X448") != 0) {
         ERR_raise(ERR_LIB_EVP, ERR_R_PASSED_INVALID_ARGUMENT);
         goto end;
     }
diff --git a/crypto/evp/p_lib.c b/crypto/evp/p_lib.c
index be15f10..668607a 100644
--- a/crypto/evp/p_lib.c
+++ b/crypto/evp/p_lib.c
@@ -50,8 +50,6 @@
 #include "internal/provider.h"
 #include "evp_local.h"
 
-#include "internal/e_os.h"                /* strcasecmp on Windows */
-
 static int pkey_set_type(EVP_PKEY *pkey, ENGINE *e, int type, const char *str,
                          int len, EVP_KEYMGMT *keymgmt);
 static void evp_pkey_free_it(EVP_PKEY *key);
@@ -1018,7 +1016,7 @@
     size_t i;
 
     for (i = 0; i < OSSL_NELEM(standard_name2type); i++) {
-        if (strcasecmp(name, standard_name2type[i].ptr) == 0)
+        if (OPENSSL_strcasecmp(name, standard_name2type[i].ptr) == 0)
             return (int)standard_name2type[i].id;
     }
 
diff --git a/crypto/ffc/ffc_dh.c b/crypto/ffc/ffc_dh.c
index cedf283..266cb30 100644
--- a/crypto/ffc/ffc_dh.c
+++ b/crypto/ffc/ffc_dh.c
@@ -10,7 +10,6 @@
 #include "internal/ffc.h"
 #include "internal/nelem.h"
 #include "crypto/bn_dh.h"
-#include "internal/e_os.h" /* strcasecmp */
 
 #ifndef OPENSSL_NO_DH
 
@@ -84,7 +83,7 @@
     size_t i;
 
     for (i = 0; i < OSSL_NELEM(dh_named_groups); ++i) {
-        if (strcasecmp(dh_named_groups[i].name, name) == 0)
+        if (OPENSSL_strcasecmp(dh_named_groups[i].name, name) == 0)
             return &dh_named_groups[i];
     }
     return NULL;
diff --git a/crypto/ffc/ffc_params.c b/crypto/ffc/ffc_params.c
index 1078a7b..500189e 100644
--- a/crypto/ffc/ffc_params.c
+++ b/crypto/ffc/ffc_params.c
@@ -12,7 +12,6 @@
 #include "internal/ffc.h"
 #include "internal/param_build_set.h"
 #include "internal/nelem.h"
-#include "internal/e_os.h" /* strcasecmp */
 
 #ifndef FIPS_MODULE
 # include <openssl/asn1.h> /* ossl_ffc_params_print */
diff --git a/crypto/http/http_client.c b/crypto/http/http_client.c
index d6345b4..8fcc9c3 100644
--- a/crypto/http/http_client.c
+++ b/crypto/http/http_client.c
@@ -321,7 +321,7 @@
 
     for (i = 0; i < sk_CONF_VALUE_num(headers); i++) {
         hdr = sk_CONF_VALUE_value(headers, i);
-        if (add_host && strcasecmp("host", hdr->name) == 0)
+        if (add_host && OPENSSL_strcasecmp("host", hdr->name) == 0)
             add_host = 0;
         if (!OSSL_HTTP_REQ_CTX_add1_header(rctx, hdr->name, hdr->value))
             return 0;
@@ -665,13 +665,13 @@
         }
         if (value != NULL && line_end != NULL) {
             if (rctx->state == OHS_REDIRECT
-                    && strcasecmp(key, "Location") == 0) {
+                    && OPENSSL_strcasecmp(key, "Location") == 0) {
                 rctx->redirection_url = value;
                 return 0;
             }
             if (rctx->expected_ct != NULL
-                    && strcasecmp(key, "Content-Type") == 0) {
-                if (strcasecmp(rctx->expected_ct, value) != 0) {
+                    && OPENSSL_strcasecmp(key, "Content-Type") == 0) {
+                if (OPENSSL_strcasecmp(rctx->expected_ct, value) != 0) {
                     ERR_raise_data(ERR_LIB_HTTP, HTTP_R_UNEXPECTED_CONTENT_TYPE,
                                    "expected=%s, actual=%s",
                                    rctx->expected_ct, value);
@@ -681,12 +681,12 @@
             }
 
             /* https://tools.ietf.org/html/rfc7230#section-6.3 Persistence */
-            if (strcasecmp(key, "Connection") == 0) {
-                if (strcasecmp(value, "keep-alive") == 0)
+            if (OPENSSL_strcasecmp(key, "Connection") == 0) {
+                if (OPENSSL_strcasecmp(value, "keep-alive") == 0)
                     found_keep_alive = 1;
-                else if (strcasecmp(value, "close") == 0)
+                else if (OPENSSL_strcasecmp(value, "close") == 0)
                     found_keep_alive = 0;
-            } else if (strcasecmp(key, "Content-Length") == 0) {
+            } else if (OPENSSL_strcasecmp(key, "Content-Length") == 0) {
                 resp_len = (size_t)strtoul(value, &line_end, 10);
                 if (line_end == value || *line_end != '\0') {
                     ERR_raise_data(ERR_LIB_HTTP,
diff --git a/crypto/objects/o_names.c b/crypto/objects/o_names.c
index 82fbc3b..e60a5a5 100644
--- a/crypto/objects/o_names.c
+++ b/crypto/objects/o_names.c
@@ -22,23 +22,6 @@
 #include "internal/e_os.h"
 
 /*
- * We define this wrapper for two reasons. Firstly, later versions of
- * DEC C add linkage information to certain functions, which makes it
- * tricky to use them as values to regular function pointers.
- * Secondly, in the EDK2 build environment, the strcasecmp function is
- * actually an external function with the Microsoft ABI, so we can't
- * transparently assign function pointers to it.
- */
-#if defined(OPENSSL_SYS_VMS_DECC) || defined(OPENSSL_SYS_UEFI)
-static int obj_strcasecmp(const char *a, const char *b)
-{
-    return strcasecmp(a, b);
-}
-#else
-#define obj_strcasecmp strcasecmp
-#endif
-
-/*
  * I use the ex_data stuff to manage the identifiers for the obj_name_types
  * that applications may define.  I only really use the free function field.
  */
@@ -111,7 +94,7 @@
             goto out;
         }
         name_funcs->hash_func = ossl_lh_strcasehash;
-        name_funcs->cmp_func = obj_strcasecmp;
+        name_funcs->cmp_func = OPENSSL_strcasecmp;
         push = sk_NAME_FUNCS_push(name_funcs_stack, name_funcs);
 
         if (!push) {
@@ -145,7 +128,7 @@
             ret = sk_NAME_FUNCS_value(name_funcs_stack,
                                       a->type)->cmp_func(a->name, b->name);
         } else
-            ret = strcasecmp(a->name, b->name);
+            ret = OPENSSL_strcasecmp(a->name, b->name);
     }
     return ret;
 }
diff --git a/crypto/params_dup.c b/crypto/params_dup.c
index 3c3b18e..eee2cc2 100644
--- a/crypto/params_dup.c
+++ b/crypto/params_dup.c
@@ -11,7 +11,6 @@
 #include <openssl/params.h>
 #include <openssl/param_build.h>
 #include "internal/param_build_set.h"
-#include "internal/e_os.h" /* strcasecmp */
 
 #define OSSL_PARAM_ALLOCATED_END    127
 #define OSSL_PARAM_MERGE_LIST_MAX   128
@@ -144,7 +143,7 @@
     const OSSL_PARAM *l = *(const OSSL_PARAM **)left;
     const OSSL_PARAM *r = *(const OSSL_PARAM **)right;
 
-    return strcasecmp(l->key, r->key);
+    return OPENSSL_strcasecmp(l->key, r->key);
 }
 
 OSSL_PARAM *OSSL_PARAM_merge(const OSSL_PARAM *p1, const OSSL_PARAM *p2)
@@ -211,7 +210,7 @@
             break;
         }
         /* consume the list element with the smaller key */
-        diff = strcasecmp((*p1cur)->key, (*p2cur)->key);
+        diff = OPENSSL_strcasecmp((*p1cur)->key, (*p2cur)->key);
         if (diff == 0) {
             /* If the keys are the same then throw away the list1 element */
             *dst++ = **p2cur;
diff --git a/crypto/property/property_parse.c b/crypto/property/property_parse.c
index 4b99ee1..6809da3 100644
--- a/crypto/property/property_parse.c
+++ b/crypto/property/property_parse.c
@@ -45,7 +45,7 @@
 {
     const char *s = *t;
 
-    if (strncasecmp(s, m, m_len) == 0) {
+    if (OPENSSL_strncasecmp(s, m, m_len) == 0) {
         *t = skip_space(s + m_len);
         return 1;
     }
diff --git a/crypto/rand/rand_lib.c b/crypto/rand/rand_lib.c
index 79f5ce3..d4e8d4f 100644
--- a/crypto/rand/rand_lib.c
+++ b/crypto/rand/rand_lib.c
@@ -766,22 +766,22 @@
 
     for (i = 0; i < sk_CONF_VALUE_num(elist); i++) {
         cval = sk_CONF_VALUE_value(elist, i);
-        if (strcasecmp(cval->name, "random") == 0) {
+        if (OPENSSL_strcasecmp(cval->name, "random") == 0) {
             if (!random_set_string(&dgbl->rng_name, cval->value))
                 return 0;
-        } else if (strcasecmp(cval->name, "cipher") == 0) {
+        } else if (OPENSSL_strcasecmp(cval->name, "cipher") == 0) {
             if (!random_set_string(&dgbl->rng_cipher, cval->value))
                 return 0;
-        } else if (strcasecmp(cval->name, "digest") == 0) {
+        } else if (OPENSSL_strcasecmp(cval->name, "digest") == 0) {
             if (!random_set_string(&dgbl->rng_digest, cval->value))
                 return 0;
-        } else if (strcasecmp(cval->name, "properties") == 0) {
+        } else if (OPENSSL_strcasecmp(cval->name, "properties") == 0) {
             if (!random_set_string(&dgbl->rng_propq, cval->value))
                 return 0;
-        } else if (strcasecmp(cval->name, "seed") == 0) {
+        } else if (OPENSSL_strcasecmp(cval->name, "seed") == 0) {
             if (!random_set_string(&dgbl->seed_name, cval->value))
                 return 0;
-        } else if (strcasecmp(cval->name, "seed_properties") == 0) {
+        } else if (OPENSSL_strcasecmp(cval->name, "seed_properties") == 0) {
             if (!random_set_string(&dgbl->seed_propq, cval->value))
                 return 0;
         } else {
diff --git a/crypto/rsa/rsa_backend.c b/crypto/rsa/rsa_backend.c
index a0e1e14..0dab302 100644
--- a/crypto/rsa/rsa_backend.c
+++ b/crypto/rsa/rsa_backend.c
@@ -27,8 +27,6 @@
 #include "crypto/rsa.h"
 #include "rsa_local.h"
 
-#include "internal/e_os.h"                /* strcasecmp for Windows() */
-
 /*
  * The intention with the "backend" source file is to offer backend support
  * for legacy backends (EVP_PKEY_ASN1_METHOD and EVP_PKEY_METHOD) and provider
@@ -275,8 +273,8 @@
         else if (!OSSL_PARAM_get_utf8_ptr(param_mgf, &mgfname))
             return 0;
 
-        if (strcasecmp(param_mgf->data,
-                       ossl_rsa_mgf_nid2name(default_maskgenalg_nid)) != 0)
+        if (OPENSSL_strcasecmp(param_mgf->data,
+                               ossl_rsa_mgf_nid2name(default_maskgenalg_nid)) != 0)
             return 0;
     }
 
diff --git a/crypto/store/store_lib.c b/crypto/store/store_lib.c
index 81e0f70..e748647 100644
--- a/crypto/store/store_lib.c
+++ b/crypto/store/store_lib.c
@@ -93,7 +93,7 @@
     OPENSSL_strlcpy(scheme_copy, uri, sizeof(scheme_copy));
     if ((p = strchr(scheme_copy, ':')) != NULL) {
         *p++ = '\0';
-        if (strcasecmp(scheme_copy, "file") != 0) {
+        if (OPENSSL_strcasecmp(scheme_copy, "file") != 0) {
             if (HAS_PREFIX(p, "//"))
                 schemes_n--;         /* Invalidate the file scheme */
             schemes[schemes_n++] = scheme_copy;
diff --git a/crypto/store/store_result.c b/crypto/store/store_result.c
index 567b9c9..64672dc 100644
--- a/crypto/store/store_result.c
+++ b/crypto/store/store_result.c
@@ -457,7 +457,7 @@
 
         /* If we have a data type, it should be a PEM name */
         if (data->data_type != NULL
-            && (strcasecmp(data->data_type, PEM_STRING_X509_TRUSTED) == 0))
+            && (OPENSSL_strcasecmp(data->data_type, PEM_STRING_X509_TRUSTED) == 0))
             ignore_trusted = 0;
 
         if (d2i_X509_AUX(&cert, (const unsigned char **)&data->octet_data,
diff --git a/crypto/trace.c b/crypto/trace.c
index a9a097f..54ee069 100644
--- a/crypto/trace.c
+++ b/crypto/trace.c
@@ -19,8 +19,6 @@
 #include "internal/refcount.h"
 #include "crypto/cryptlib.h"
 
-#include "internal/e_os.h"                /* strcasecmp for Windows */
-
 #ifndef OPENSSL_NO_TRACE
 
 static CRYPTO_RWLOCK *trace_lock = NULL;
@@ -158,7 +156,7 @@
     size_t i;
 
     for (i = 0; i < OSSL_NELEM(trace_categories); i++)
-        if (strcasecmp(name, trace_categories[i].name) == 0)
+        if (OPENSSL_strcasecmp(name, trace_categories[i].name) == 0)
             return trace_categories[i].num;
     return -1; /* not found */
 }
diff --git a/crypto/x509/v3_tlsf.c b/crypto/x509/v3_tlsf.c
index 32ac300..7302e02 100644
--- a/crypto/x509/v3_tlsf.c
+++ b/crypto/x509/v3_tlsf.c
@@ -108,7 +108,7 @@
             extval = val->name;
 
         for (j = 0; j < OSSL_NELEM(tls_feature_tbl); j++)
-            if (strcasecmp(extval, tls_feature_tbl[j].name) == 0)
+            if (OPENSSL_strcasecmp(extval, tls_feature_tbl[j].name) == 0)
                 break;
         if (j < OSSL_NELEM(tls_feature_tbl))
             tlsextid = tls_feature_tbl[j].num;
diff --git a/engines/e_devcrypto.c b/engines/e_devcrypto.c
index abc2930..5c547dd 100644
--- a/engines/e_devcrypto.c
+++ b/engines/e_devcrypto.c
@@ -1159,9 +1159,9 @@
     case DEVCRYPTO_CMD_CIPHERS:
         if (p == NULL)
             return 1;
-        if (strcasecmp((const char *)p, "ALL") == 0) {
+        if (OPENSSL_strcasecmp((const char *)p, "ALL") == 0) {
             devcrypto_select_all_ciphers(selected_ciphers);
-        } else if (strcasecmp((const char*)p, "NONE") == 0) {
+        } else if (OPENSSL_strcasecmp((const char*)p, "NONE") == 0) {
             memset(selected_ciphers, 0, sizeof(selected_ciphers));
         } else {
             new_list=OPENSSL_zalloc(sizeof(selected_ciphers));
@@ -1179,9 +1179,9 @@
     case DEVCRYPTO_CMD_DIGESTS:
         if (p == NULL)
             return 1;
-        if (strcasecmp((const char *)p, "ALL") == 0) {
+        if (OPENSSL_strcasecmp((const char *)p, "ALL") == 0) {
             devcrypto_select_all_digests(selected_digests);
-        } else if (strcasecmp((const char*)p, "NONE") == 0) {
+        } else if (OPENSSL_strcasecmp((const char*)p, "NONE") == 0) {
             memset(selected_digests, 0, sizeof(selected_digests));
         } else {
             new_list=OPENSSL_zalloc(sizeof(selected_digests));
diff --git a/engines/e_loader_attic.c b/engines/e_loader_attic.c
index be36c6e..b467220 100644
--- a/engines/e_loader_attic.c
+++ b/engines/e_loader_attic.c
@@ -14,7 +14,7 @@
 /* We need to use some engine deprecated APIs */
 #define OPENSSL_SUPPRESS_DEPRECATED
 
-#include "internal/e_os.h" /* for stat and strncasecmp */
+#include "internal/e_os.h" /* for stat */
 #include <string.h>
 #include <sys/stat.h>
 #include <ctype.h>
@@ -1459,7 +1459,8 @@
     /*
      * First, check the basename
      */
-    if (strncasecmp(name, ctx->_.dir.search_name, len) != 0 || name[len] != '.')
+    if (OPENSSL_strncasecmp(name, ctx->_.dir.search_name, len) != 0
+        || name[len] != '.')
         return 0;
     p = &name[len + 1];
 
diff --git a/include/internal/common.h b/include/internal/common.h
index f20b041..9f8746b 100644
--- a/include/internal/common.h
+++ b/include/internal/common.h
@@ -13,8 +13,8 @@
 
 # include <stdlib.h>
 # include <string.h>
-# include "internal/e_os.h" /* To get strncasecmp() on Windows */
 
+# include "internal/e_os.h" /* ossl_inline in many files */
 # include "internal/nelem.h"
 
 #ifdef NDEBUG
@@ -40,13 +40,13 @@
 #define CHECK_AND_SKIP_PREFIX(str, pre) \
     (HAS_PREFIX(str, pre) ? ((str) += sizeof(pre) - 1, 1) : 0)
 /* Check if the string literal |p| is a case-insensitive prefix of |s| */
-#define HAS_CASE_PREFIX(s, p) (strncasecmp(s, p "", sizeof(p) - 1) == 0)
+#define HAS_CASE_PREFIX(s, p) (OPENSSL_strncasecmp(s, p "", sizeof(p) - 1) == 0)
 /* As before, and if check succeeds, advance |str| past the prefix |pre| */
 #define CHECK_AND_SKIP_CASE_PREFIX(str, pre) \
     (HAS_CASE_PREFIX(str, pre) ? ((str) += sizeof(pre) - 1, 1) : 0)
 /* Check if the string literal |suffix| is a case-insensitive suffix of |str| */
 #define HAS_CASE_SUFFIX(str, suffix) (strlen(str) < sizeof(suffix) - 1 ? 0 : \
-    strcasecmp(str + strlen(str) - sizeof(suffix) + 1, suffix "") == 0)
+    OPENSSL_strcasecmp(str + strlen(str) - sizeof(suffix) + 1, suffix "") == 0)
 
 /*
  * Use this inside a union with the field that needs to be aligned to a
diff --git a/providers/common/capabilities.c b/providers/common/capabilities.c
index edf7c9f..63d531b 100644
--- a/providers/common/capabilities.c
+++ b/providers/common/capabilities.c
@@ -217,7 +217,7 @@
 int ossl_prov_get_capabilities(void *provctx, const char *capability,
                                OSSL_CALLBACK *cb, void *arg)
 {
-    if (strcasecmp(capability, "TLS-GROUP") == 0)
+    if (OPENSSL_strcasecmp(capability, "TLS-GROUP") == 0)
         return tls_group_capability(cb, arg);
 
     /* We don't support this capability */
diff --git a/providers/implementations/ciphers/cipher_cts.c b/providers/implementations/ciphers/cipher_cts.c
index aced202..5c48f37 100644
--- a/providers/implementations/ciphers/cipher_cts.c
+++ b/providers/implementations/ciphers/cipher_cts.c
@@ -46,7 +46,6 @@
  *      Otherwise it is the same as CS2.
  */
 
-#include "internal/e_os.h" /* strcasecmp */
 #include <openssl/core_names.h>
 #include "prov/ciphercommon.h"
 #include "internal/nelem.h"
@@ -92,7 +91,7 @@
     size_t i;
 
     for (i = 0; i < OSSL_NELEM(cts_modes); ++i) {
-        if (strcasecmp(name, cts_modes[i].name) == 0)
+        if (OPENSSL_strcasecmp(name, cts_modes[i].name) == 0)
             return (int)cts_modes[i].id;
     }
     return -1;
diff --git a/providers/implementations/kdfs/hkdf.c b/providers/implementations/kdfs/hkdf.c
index 2238c32..1223d95 100644
--- a/providers/implementations/kdfs/hkdf.c
+++ b/providers/implementations/kdfs/hkdf.c
@@ -230,11 +230,11 @@
 
     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_MODE)) != NULL) {
         if (p->data_type == OSSL_PARAM_UTF8_STRING) {
-            if (strcasecmp(p->data, "EXTRACT_AND_EXPAND") == 0) {
+            if (OPENSSL_strcasecmp(p->data, "EXTRACT_AND_EXPAND") == 0) {
                 ctx->mode = EVP_KDF_HKDF_MODE_EXTRACT_AND_EXPAND;
-            } else if (strcasecmp(p->data, "EXTRACT_ONLY") == 0) {
+            } else if (OPENSSL_strcasecmp(p->data, "EXTRACT_ONLY") == 0) {
                 ctx->mode = EVP_KDF_HKDF_MODE_EXTRACT_ONLY;
-            } else if (strcasecmp(p->data, "EXPAND_ONLY") == 0) {
+            } else if (OPENSSL_strcasecmp(p->data, "EXPAND_ONLY") == 0) {
                 ctx->mode = EVP_KDF_HKDF_MODE_EXPAND_ONLY;
             } else {
                 ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_MODE);
diff --git a/providers/implementations/kdfs/kbkdf.c b/providers/implementations/kdfs/kbkdf.c
index 7462eb6..c9ad0de 100644
--- a/providers/implementations/kdfs/kbkdf.c
+++ b/providers/implementations/kdfs/kbkdf.c
@@ -341,10 +341,11 @@
     }
 
     p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_MODE);
-    if (p != NULL && strncasecmp("counter", p->data, p->data_size) == 0) {
+    if (p != NULL
+        && OPENSSL_strncasecmp("counter", p->data, p->data_size) == 0) {
         ctx->mode = COUNTER;
     } else if (p != NULL
-               && strncasecmp("feedback", p->data, p->data_size) == 0) {
+               && OPENSSL_strncasecmp("feedback", p->data, p->data_size) == 0) {
         ctx->mode = FEEDBACK;
     } else if (p != NULL) {
         ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_MODE);
diff --git a/providers/implementations/kdfs/tls1_prf.c b/providers/implementations/kdfs/tls1_prf.c
index eba4da5..e194ecc 100644
--- a/providers/implementations/kdfs/tls1_prf.c
+++ b/providers/implementations/kdfs/tls1_prf.c
@@ -198,7 +198,7 @@
         return 1;
 
     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_DIGEST)) != NULL) {
-        if (strcasecmp(p->data, SN_md5_sha1) == 0) {
+        if (OPENSSL_strcasecmp(p->data, SN_md5_sha1) == 0) {
             if (!ossl_prov_macctx_load_from_params(&ctx->P_hash, params,
                                                    OSSL_MAC_NAME_HMAC,
                                                    NULL, SN_md5, libctx)
diff --git a/providers/implementations/kem/rsa_kem.c b/providers/implementations/kem/rsa_kem.c
index 201c80e..bfc3da6 100644
--- a/providers/implementations/kem/rsa_kem.c
+++ b/providers/implementations/kem/rsa_kem.c
@@ -12,8 +12,8 @@
  * internal use.
  */
 #include "internal/deprecated.h"
+#include "internal/nelem.h"
 
-#include "internal/e_os.h"  /* strcasecmp */
 #include <openssl/crypto.h>
 #include <openssl/evp.h>
 #include <openssl/core_dispatch.h>
@@ -69,7 +69,7 @@
         return -1;
 
     for (i = 0; i < sz; ++i) {
-        if (strcasecmp(map[i].ptr, name) == 0)
+        if (OPENSSL_strcasecmp(map[i].ptr, name) == 0)
             return map[i].id;
     }
     return -1;
diff --git a/providers/implementations/keymgmt/dsa_kmgmt.c b/providers/implementations/keymgmt/dsa_kmgmt.c
index 3ddafbd..ec5cb5f 100644
--- a/providers/implementations/keymgmt/dsa_kmgmt.c
+++ b/providers/implementations/keymgmt/dsa_kmgmt.c
@@ -13,7 +13,6 @@
  */
 #include "internal/deprecated.h"
 
-#include "internal/e_os.h" /* strcasecmp */
 #include <openssl/core_dispatch.h>
 #include <openssl/core_names.h>
 #include <openssl/bn.h>
@@ -90,7 +89,7 @@
     size_t i;
 
     for (i = 0; i < OSSL_NELEM(dsatype2id); ++i) {
-        if (strcasecmp(dsatype2id[i].name, name) == 0)
+        if (OPENSSL_strcasecmp(dsatype2id[i].name, name) == 0)
             return dsatype2id[i].id;
     }
     return -1;
diff --git a/providers/implementations/keymgmt/ec_kmgmt.c b/providers/implementations/keymgmt/ec_kmgmt.c
index 8a86c91..e72b0c3 100644
--- a/providers/implementations/keymgmt/ec_kmgmt.c
+++ b/providers/implementations/keymgmt/ec_kmgmt.c
@@ -13,7 +13,6 @@
  */
 #include "internal/deprecated.h"
 
-#include "internal/e_os.h" /* strcasecmp */
 #include <string.h>
 #include <openssl/core_dispatch.h>
 #include <openssl/core_names.h>
diff --git a/providers/implementations/keymgmt/ecx_kmgmt.c b/providers/implementations/keymgmt/ecx_kmgmt.c
index 9afcb6d..333f2b7 100644
--- a/providers/implementations/keymgmt/ecx_kmgmt.c
+++ b/providers/implementations/keymgmt/ecx_kmgmt.c
@@ -9,8 +9,6 @@
 
 #include <assert.h>
 #include <string.h>
-/* For strcasecmp on Windows */
-#include "internal/e_os.h"
 #include <openssl/core_dispatch.h>
 #include <openssl/core_names.h>
 #include <openssl/params.h>
@@ -546,7 +544,7 @@
         }
         if (p->data_type != OSSL_PARAM_UTF8_STRING
                 || groupname == NULL
-                || strcasecmp(p->data, groupname) != 0) {
+                || OPENSSL_strcasecmp(p->data, groupname) != 0) {
             ERR_raise(ERR_LIB_PROV, ERR_R_PASSED_INVALID_ARGUMENT);
             return 0;
         }
diff --git a/providers/implementations/keymgmt/mac_legacy_kmgmt.c b/providers/implementations/keymgmt/mac_legacy_kmgmt.c
index 73af207..653d9c6 100644
--- a/providers/implementations/keymgmt/mac_legacy_kmgmt.c
+++ b/providers/implementations/keymgmt/mac_legacy_kmgmt.c
@@ -26,7 +26,6 @@
 #include "prov/providercommon.h"
 #include "prov/provider_ctx.h"
 #include "prov/macsignature.h"
-#include "internal/e_os.h" /* strcasecmp */
 
 static OSSL_FUNC_keymgmt_new_fn mac_new;
 static OSSL_FUNC_keymgmt_free_fn mac_free;
diff --git a/providers/implementations/rands/drbg_ctr.c b/providers/implementations/rands/drbg_ctr.c
index 1384a43..c51eb4b 100644
--- a/providers/implementations/rands/drbg_ctr.c
+++ b/providers/implementations/rands/drbg_ctr.c
@@ -14,7 +14,6 @@
 #include <openssl/rand.h>
 #include <openssl/aes.h>
 #include <openssl/proverr.h>
-#include "internal/e_os.h" /* strcasecmp */
 #include "crypto/modes.h"
 #include "internal/thread_once.h"
 #include "prov/implementations.h"
@@ -690,7 +689,7 @@
         if (p->data_type != OSSL_PARAM_UTF8_STRING
                 || p->data_size < ctr_str_len)
             return 0;
-        if (strcasecmp("CTR", base + p->data_size - ctr_str_len) != 0) {
+        if (OPENSSL_strcasecmp("CTR", base + p->data_size - ctr_str_len) != 0) {
             ERR_raise(ERR_LIB_PROV, PROV_R_REQUIRE_CTR_MODE_CIPHER);
             return 0;
         }
diff --git a/providers/implementations/signature/rsa_sig.c b/providers/implementations/signature/rsa_sig.c
index f543bdb..54051be 100644
--- a/providers/implementations/signature/rsa_sig.c
+++ b/providers/implementations/signature/rsa_sig.c
@@ -13,7 +13,6 @@
  */
 #include "internal/deprecated.h"
 
-#include "internal/e_os.h" /* strcasecmp */
 #include <string.h>
 #include <openssl/crypto.h>
 #include <openssl/core_dispatch.h>
@@ -854,7 +853,7 @@
 
     if (mdname != NULL
         /* was rsa_setup_md already called in rsa_signverify_init()? */
-        && (mdname[0] == '\0' || strcasecmp(prsactx->mdname, mdname) != 0)
+        && (mdname[0] == '\0' || OPENSSL_strcasecmp(prsactx->mdname, mdname) != 0)
         && !rsa_setup_md(prsactx, mdname, prsactx->propq))
         return 0;
 
diff --git a/providers/implementations/storemgmt/file_store.c b/providers/implementations/storemgmt/file_store.c
index 461b7e4..68c75a0 100644
--- a/providers/implementations/storemgmt/file_store.c
+++ b/providers/implementations/storemgmt/file_store.c
@@ -9,8 +9,6 @@
 
 /* This file has quite some overlap with engines/e_loader_attic.c */
 
-#include "internal/e_os.h"                /* To get strncasecmp() on Windows */
-
 #include <string.h>
 #include <sys/stat.h>
 #include <ctype.h>  /* isdigit */
@@ -590,7 +588,8 @@
     /*
      * First, check the basename
      */
-    if (strncasecmp(name, ctx->_.dir.search_name, len) != 0 || name[len] != '.')
+    if (OPENSSL_strncasecmp(name, ctx->_.dir.search_name, len) != 0
+        || name[len] != '.')
         return 0;
     p = &name[len + 1];
 
diff --git a/ssl/ssl_conf.c b/ssl/ssl_conf.c
index 6baf0e6..f333792 100644
--- a/ssl/ssl_conf.c
+++ b/ssl/ssl_conf.c
@@ -148,7 +148,8 @@
     if (namelen == -1) {
         if (strcmp(tbl->name, name))
             return 0;
-    } else if (tbl->namelen != namelen || strncasecmp(tbl->name, name, namelen))
+    } else if (tbl->namelen != namelen
+               || OPENSSL_strncasecmp(tbl->name, name, namelen))
         return 0;
     ssl_set_option(cctx, tbl->name_flags, tbl->option_value, onoff);
     return 1;
@@ -232,8 +233,8 @@
 
     /* Ignore values supported by 1.0.2 for the automatic selection */
     if ((cctx->flags & SSL_CONF_FLAG_FILE)
-            && (strcasecmp(value, "+automatic") == 0
-                || strcasecmp(value, "automatic") == 0))
+            && (OPENSSL_strcasecmp(value, "+automatic") == 0
+                || OPENSSL_strcasecmp(value, "automatic") == 0))
         return 1;
     if ((cctx->flags & SSL_CONF_FLAG_CMDLINE) &&
         strcmp(value, "auto") == 0)
@@ -815,7 +816,7 @@
             strncmp(*pcmd, cctx->prefix, cctx->prefixlen))
             return 0;
         if (cctx->flags & SSL_CONF_FLAG_FILE &&
-            strncasecmp(*pcmd, cctx->prefix, cctx->prefixlen))
+            OPENSSL_strncasecmp(*pcmd, cctx->prefix, cctx->prefixlen))
             return 0;
         *pcmd += cctx->prefixlen;
     } else if (cctx->flags & SSL_CONF_FLAG_CMDLINE) {
@@ -857,7 +858,7 @@
                     return t;
             }
             if (cctx->flags & SSL_CONF_FLAG_FILE) {
-                if (t->str_file && strcasecmp(t->str_file, cmd) == 0)
+                if (t->str_file && OPENSSL_strcasecmp(t->str_file, cmd) == 0)
                     return t;
             }
         }
diff --git a/test/bntest.c b/test/bntest.c
index 62ca283..73a7dba 100644
--- a/test/bntest.c
+++ b/test/bntest.c
@@ -23,10 +23,6 @@
 #include "internal/numbers.h"
 #include "testutil.h"
 
-#ifdef OPENSSL_SYS_WINDOWS
-# define strcasecmp _stricmp
-#endif
-
 /*
  * Things in boring, not in openssl.
  */
@@ -64,7 +60,7 @@
     PAIR *pp = s->pairs;
 
     for ( ; --i >= 0; pp++)
-        if (strcasecmp(pp->key, key) == 0)
+        if (OPENSSL_strcasecmp(pp->key, key) == 0)
             return pp->value;
     return NULL;
 }
diff --git a/test/evp_extra_test.c b/test/evp_extra_test.c
index d8dafef..6db12e6 100644
--- a/test/evp_extra_test.c
+++ b/test/evp_extra_test.c
@@ -35,7 +35,6 @@
 #include "internal/nelem.h"
 #include "internal/sizes.h"
 #include "crypto/evp.h"
-#include "internal/e_os.h" /* strcasecmp */
 
 static OSSL_LIB_CTX *testctx = NULL;
 static char *testpropq = NULL;
@@ -1739,7 +1738,7 @@
         return 0;
 
     for (i = 0; i < OSSL_NELEM(ec_encodings); i++) {
-        if (strcasecmp(enc_name, ec_encodings[i].encoding_name) == 0) {
+        if (OPENSSL_strcasecmp(enc_name, ec_encodings[i].encoding_name) == 0) {
             *enc = ec_encodings[i].encoding;
             break;
         }
diff --git a/test/evp_libctx_test.c b/test/evp_libctx_test.c
index ada3bf0..9b2f4a0 100644
--- a/test/evp_libctx_test.c
+++ b/test/evp_libctx_test.c
@@ -33,7 +33,6 @@
 #include "testutil.h"
 #include "internal/nelem.h"
 #include "crypto/bn_dh.h"   /* _bignum_ffdhe2048_p */
-#include "internal/e_os.h"        /* strcasecmp */
 
 static OSSL_LIB_CTX *libctx = NULL;
 static OSSL_PROVIDER *nullprov = NULL;
@@ -478,7 +477,7 @@
 
 static int name_cmp(const char * const *a, const char * const *b)
 {
-    return strcasecmp(*a, *b);
+    return OPENSSL_strcasecmp(*a, *b);
 }
 
 static void collect_cipher_names(EVP_CIPHER *cipher, void *cipher_names_list)
diff --git a/test/evp_test.c b/test/evp_test.c
index b846a59..61526ff 100644
--- a/test/evp_test.c
+++ b/test/evp_test.c
@@ -12,7 +12,6 @@
 #include <string.h>
 #include <stdlib.h>
 #include <ctype.h>
-#include "internal/e_os.h" /* strcasecmp and strncasecmp */
 #include <openssl/evp.h>
 #include <openssl/pem.h>
 #include <openssl/err.h>
@@ -3967,31 +3966,31 @@
         return 1;
 #endif
 #ifdef OPENSSL_NO_MD2
-    if (strcasecmp(name, "MD2") == 0)
+    if (OPENSSL_strcasecmp(name, "MD2") == 0)
         return 1;
 #endif
 #ifdef OPENSSL_NO_MDC2
-    if (strcasecmp(name, "MDC2") == 0)
+    if (OPENSSL_strcasecmp(name, "MDC2") == 0)
         return 1;
 #endif
 #ifdef OPENSSL_NO_MD4
-    if (strcasecmp(name, "MD4") == 0)
+    if (OPENSSL_strcasecmp(name, "MD4") == 0)
         return 1;
 #endif
 #ifdef OPENSSL_NO_MD5
-    if (strcasecmp(name, "MD5") == 0)
+    if (OPENSSL_strcasecmp(name, "MD5") == 0)
         return 1;
 #endif
 #ifdef OPENSSL_NO_RMD160
-    if (strcasecmp(name, "RIPEMD160") == 0)
+    if (OPENSSL_strcasecmp(name, "RIPEMD160") == 0)
         return 1;
 #endif
 #ifdef OPENSSL_NO_SM3
-    if (strcasecmp(name, "SM3") == 0)
+    if (OPENSSL_strcasecmp(name, "SM3") == 0)
         return 1;
 #endif
 #ifdef OPENSSL_NO_WHIRLPOOL
-    if (strcasecmp(name, "WHIRLPOOL") == 0)
+    if (OPENSSL_strcasecmp(name, "WHIRLPOOL") == 0)
         return 1;
 #endif
     return 0;
diff --git a/test/helpers/ssl_test_ctx.c b/test/helpers/ssl_test_ctx.c
index 1374b04..7236ffd 100644
--- a/test/helpers/ssl_test_ctx.c
+++ b/test/helpers/ssl_test_ctx.c
@@ -16,21 +16,17 @@
 #include "ssl_test_ctx.h"
 #include "../testutil.h"
 
-#ifdef OPENSSL_SYS_WINDOWS
-# define strcasecmp _stricmp
-#endif
-
 static const int default_app_data_size = 256;
 /* Default set to be as small as possible to exercise fragmentation. */
 static const int default_max_fragment_size = 512;
 
 static int parse_boolean(const char *value, int *result)
 {
-    if (strcasecmp(value, "Yes") == 0) {
+    if (OPENSSL_strcasecmp(value, "Yes") == 0) {
         *result = 1;
         return 1;
     }
-    else if (strcasecmp(value, "No") == 0) {
+    else if (OPENSSL_strcasecmp(value, "No") == 0) {
         *result = 0;
         return 1;
     }
diff --git a/test/params_conversion_test.c b/test/params_conversion_test.c
index 01f9400..48e20e5 100644
--- a/test/params_conversion_test.c
+++ b/test/params_conversion_test.c
@@ -15,10 +15,6 @@
 /* On machines that dont support <inttypes.h> just disable the tests */
 #if !defined(OPENSSL_NO_INTTYPES_H)
 
-# ifdef OPENSSL_SYS_WINDOWS
-#  define strcasecmp _stricmp
-# endif
-
 # ifdef OPENSSL_SYS_VMS
 #  define strtoumax strtoull
 #  define strtoimax strtoll
@@ -62,7 +58,7 @@
 
     for (i = 0; i < s->numpairs; i++, pp++) {
         p = "";
-        if (strcasecmp(pp->key, "type") == 0) {
+        if (OPENSSL_strcasecmp(pp->key, "type") == 0) {
             if (type != NULL) {
                 TEST_info("Line %d: multiple type lines", s->curr);
                 return 0;
@@ -72,48 +68,48 @@
                 TEST_info("Line %d: unknown type line", s->curr);
                 return 0;
             }
-        } else if (strcasecmp(pp->key, "int32") == 0) {
+        } else if (OPENSSL_strcasecmp(pp->key, "int32") == 0) {
             if (def_i32++) {
                 TEST_info("Line %d: multiple int32 lines", s->curr);
                 return 0;
             }
-            if (strcasecmp(pp->value, "invalid") != 0) {
+            if (OPENSSL_strcasecmp(pp->value, "invalid") != 0) {
                 pc->valid_i32 = 1;
                 pc->i32 = (int32_t)strtoimax(pp->value, &p, 10);
             }
-        } else if (strcasecmp(pp->key, "int64") == 0) {
+        } else if (OPENSSL_strcasecmp(pp->key, "int64") == 0) {
             if (def_i64++) {
                 TEST_info("Line %d: multiple int64 lines", s->curr);
                 return 0;
             }
-            if (strcasecmp(pp->value, "invalid") != 0) {
+            if (OPENSSL_strcasecmp(pp->value, "invalid") != 0) {
                 pc->valid_i64 = 1;
                 pc->i64 = (int64_t)strtoimax(pp->value, &p, 10);
             }
-        } else if (strcasecmp(pp->key, "uint32") == 0) {
+        } else if (OPENSSL_strcasecmp(pp->key, "uint32") == 0) {
             if (def_u32++) {
                 TEST_info("Line %d: multiple uint32 lines", s->curr);
                 return 0;
             }
-            if (strcasecmp(pp->value, "invalid") != 0) {
+            if (OPENSSL_strcasecmp(pp->value, "invalid") != 0) {
                 pc->valid_u32 = 1;
                 pc->u32 = (uint32_t)strtoumax(pp->value, &p, 10);
             }
-        } else if (strcasecmp(pp->key, "uint64") == 0) {
+        } else if (OPENSSL_strcasecmp(pp->key, "uint64") == 0) {
             if (def_u64++) {
                 TEST_info("Line %d: multiple uint64 lines", s->curr);
                 return 0;
             }
-            if (strcasecmp(pp->value, "invalid") != 0) {
+            if (OPENSSL_strcasecmp(pp->value, "invalid") != 0) {
                 pc->valid_u64 = 1;
                 pc->u64 = (uint64_t)strtoumax(pp->value, &p, 10);
             }
-        } else if (strcasecmp(pp->key, "double") == 0) {
+        } else if (OPENSSL_strcasecmp(pp->key, "double") == 0) {
             if (def_d++) {
                 TEST_info("Line %d: multiple double lines", s->curr);
                 return 0;
             }
-            if (strcasecmp(pp->value, "invalid") != 0) {
+            if (OPENSSL_strcasecmp(pp->value, "invalid") != 0) {
                 pc->valid_d = 1;
                 pc->d = strtod(pp->value, &p);
             }
@@ -133,7 +129,7 @@
         return 0;
     }
 
-    if (strcasecmp(type, "int32") == 0) {
+    if (OPENSSL_strcasecmp(type, "int32") == 0) {
         if (!TEST_true(def_i32) || !TEST_true(pc->valid_i32)) {
             TEST_note("errant int32 on line %d", s->curr);
             return 0;
@@ -142,7 +138,7 @@
         pc->datum = &datum_i32;
         pc->ref = &ref_i32;
         pc->size = sizeof(ref_i32);
-    } else if (strcasecmp(type, "int64") == 0) {
+    } else if (OPENSSL_strcasecmp(type, "int64") == 0) {
         if (!TEST_true(def_i64) || !TEST_true(pc->valid_i64)) {
             TEST_note("errant int64 on line %d", s->curr);
             return 0;
@@ -151,7 +147,7 @@
         pc->datum = &datum_i64;
         pc->ref = &ref_i64;
         pc->size = sizeof(ref_i64);
-    } else if (strcasecmp(type, "uint32") == 0) {
+    } else if (OPENSSL_strcasecmp(type, "uint32") == 0) {
         if (!TEST_true(def_u32) || !TEST_true(pc->valid_u32)) {
             TEST_note("errant uint32 on line %d", s->curr);
             return 0;
@@ -160,7 +156,7 @@
         pc->datum = &datum_u32;
         pc->ref = &ref_u32;
         pc->size = sizeof(ref_u32);
-    } else if (strcasecmp(type, "uint64") == 0) {
+    } else if (OPENSSL_strcasecmp(type, "uint64") == 0) {
         if (!TEST_true(def_u64) || !TEST_true(pc->valid_u64)) {
             TEST_note("errant uint64 on line %d", s->curr);
             return 0;
@@ -169,7 +165,7 @@
         pc->datum = &datum_u64;
         pc->ref = &ref_u64;
         pc->size = sizeof(ref_u64);
-    } else if (strcasecmp(type, "double") == 0) {
+    } else if (OPENSSL_strcasecmp(type, "double") == 0) {
         if (!TEST_true(def_d) || !TEST_true(pc->valid_d)) {
             TEST_note("errant double on line %d", s->curr);
             return 0;
diff --git a/test/ssl_old_test.c b/test/ssl_old_test.c
index 0e75111..2c249e8 100644
--- a/test/ssl_old_test.c
+++ b/test/ssl_old_test.c
@@ -216,7 +216,7 @@
 
     if (servername) {
         if (s_ctx2 != NULL && sn_server2 != NULL &&
-            !strcasecmp(servername, sn_server2)) {
+            !OPENSSL_strcasecmp(servername, sn_server2)) {
             BIO_printf(bio_stdout, "Switching server context.\n");
             SSL_set_SSL_CTX(s, s_ctx2);
         }
diff --git a/test/v3nametest.c b/test/v3nametest.c
index 06d713b..ce1f494 100644
--- a/test/v3nametest.c
+++ b/test/v3nametest.c
@@ -15,10 +15,6 @@
 #include "internal/nelem.h"
 #include "testutil.h"
 
-#ifdef OPENSSL_SYS_WINDOWS
-# define strcasecmp _stricmp
-#endif
-
 static const char *const names[] = {
     "a", "b", ".", "*", "@",
     ".a", "a.", ".b", "b.", ".*", "*.", "*@", "@*", "a@", "@a", "b@", "..",
@@ -287,7 +283,7 @@
     int failed = 0;
 
     for (; *pname != NULL; ++pname) {
-        int samename = strcasecmp(nameincert, *pname) == 0;
+        int samename = OPENSSL_strcasecmp(nameincert, *pname) == 0;
         size_t namelen = strlen(*pname);
         char *name = OPENSSL_malloc(namelen + 1);
         int match, ret;