diff --git a/.gitignore b/.gitignore
index ab3cb76..d0a80b8 100644
--- a/.gitignore
+++ b/.gitignore
@@ -14,3 +14,5 @@
 
 # Include when developing application packages.
 pubspec.lock
+
+node_modules
diff --git a/README.md b/README.md
index 54d84f3..380ed2c 100644
--- a/README.md
+++ b/README.md
@@ -22,3 +22,8 @@
 
 Credit goes to the Dart team for creating Dart, dart2js, and the original
 preamble which this is derived from.
+
+## Contributing
+
+The only file that we directly modify is `preamble.js`. After that, to reflect your changes in
+both `preamble.dart` and `preamble.min.js`, run `npm install && npm run minify`
\ No newline at end of file
diff --git a/lib/preamble.dart b/lib/preamble.dart
index 5be025c..ab859f6 100644
--- a/lib/preamble.dart
+++ b/lib/preamble.dart
@@ -1,6 +1,6 @@
 library node_preamble;
 
-final _minified = r"""var dartNodePreambleSelf="undefined"!=typeof global?global:window,self=Object.create(dartNodePreambleSelf);if(self.scheduleImmediate=self.setImmediate?function(e){dartNodePreambleSelf.setImmediate(e)}:function(e){setTimeout(e,0)},self.require=require,self.exports=exports,"undefined"!=typeof process&&(self.process=process),"undefined"!=typeof __dirname&&(self.__dirname=__dirname),"undefined"!=typeof __filename&&(self.__filename=__filename),!dartNodePreambleSelf.window){var url="undefined"!=typeof __non_webpack_require__?__non_webpack_require__("url"):require("url");self.location={get href(){return url.pathToFileURL?url.pathToFileURL(process.cwd()).href+"/":"file://"+(e=process.cwd(),"win32"!=process.platform?e:"/"+e.replace(/\\/g,"/"))+"/";var e}},function(){function e(){try{throw new Error}catch(t){var e=t.stack,r=new RegExp("^ *at [^(]*\\((.*):[0-9]*:[0-9]*\\)$","mg"),l=null;do{var n=r.exec(e);null!=n&&(l=n)}while(null!=n);return l[1]}}var r=null;self.document={get currentScript(){return null==r&&(r={src:e()}),r}}}(),self.dartDeferredLibraryLoader=function(e,r,l){try{load(e),r()}catch(e){l(e)}}}""";
+final _minified = r"""var dartNodePreambleSelf="undefined"!=typeof global?global:window,self=Object.create(dartNodePreambleSelf);if(self.scheduleImmediate=self.setImmediate?function(e){dartNodePreambleSelf.setImmediate(e)}:function(e){setTimeout(e,0)},self.require=require,self.exports=exports,"undefined"!=typeof process)self.process=process;if("undefined"!=typeof __dirname)self.__dirname=__dirname;if("undefined"!=typeof __filename)self.__filename=__filename;if(!dartNodePreambleSelf.window){var url="undefined"!=typeof __non_webpack_require__?__non_webpack_require__("url"):require(1?"url":null);self.location={get href(){if(url.pathToFileURL)return url.pathToFileURL(process.cwd()).href+"/";else return"file://"+function(){var e=process.cwd();if("win32"!=process.platform)return e;else return"/"+e.replace(/\\/g,"/")}()+"/"}},function(){function e(){try{throw new Error}catch(t){var e=t.stack,r=new RegExp("^ *at [^(]*\\((.*):[0-9]*:[0-9]*\\)$","mg"),l=null;do{var n=r.exec(e);if(null!=n)l=n}while(null!=n);return l[1]}}var r=null;self.document={get currentScript(){if(null==r)r={src:e()};return r}}}(),self.dartDeferredLibraryLoader=function(e,r,l){try{load(e),r()}catch(e){l(e)}}}""";
 
 final _normal = r"""
 // make sure to keep this as 'var'
diff --git a/lib/preamble.min.js b/lib/preamble.min.js
index 0f97665..a888a8c 100644
--- a/lib/preamble.min.js
+++ b/lib/preamble.min.js
@@ -1 +1 @@
-var dartNodePreambleSelf="undefined"!=typeof global?global:window,self=Object.create(dartNodePreambleSelf);if(self.scheduleImmediate=self.setImmediate?function(e){dartNodePreambleSelf.setImmediate(e)}:function(e){setTimeout(e,0)},self.require=require,self.exports=exports,"undefined"!=typeof process&&(self.process=process),"undefined"!=typeof __dirname&&(self.__dirname=__dirname),"undefined"!=typeof __filename&&(self.__filename=__filename),!dartNodePreambleSelf.window){var url="undefined"!=typeof __non_webpack_require__?__non_webpack_require__("url"):require("url");self.location={get href(){return url.pathToFileURL?url.pathToFileURL(process.cwd()).href+"/":"file://"+(e=process.cwd(),"win32"!=process.platform?e:"/"+e.replace(/\\/g,"/"))+"/";var e}},function(){function e(){try{throw new Error}catch(t){var e=t.stack,r=new RegExp("^ *at [^(]*\\((.*):[0-9]*:[0-9]*\\)$","mg"),l=null;do{var n=r.exec(e);null!=n&&(l=n)}while(null!=n);return l[1]}}var r=null;self.document={get currentScript(){return null==r&&(r={src:e()}),r}}}(),self.dartDeferredLibraryLoader=function(e,r,l){try{load(e),r()}catch(e){l(e)}}}
\ No newline at end of file
+var dartNodePreambleSelf="undefined"!=typeof global?global:window,self=Object.create(dartNodePreambleSelf);if(self.scheduleImmediate=self.setImmediate?function(e){dartNodePreambleSelf.setImmediate(e)}:function(e){setTimeout(e,0)},self.require=require,self.exports=exports,"undefined"!=typeof process)self.process=process;if("undefined"!=typeof __dirname)self.__dirname=__dirname;if("undefined"!=typeof __filename)self.__filename=__filename;if(!dartNodePreambleSelf.window){var url="undefined"!=typeof __non_webpack_require__?__non_webpack_require__("url"):require(1?"url":null);self.location={get href(){if(url.pathToFileURL)return url.pathToFileURL(process.cwd()).href+"/";else return"file://"+function(){var e=process.cwd();if("win32"!=process.platform)return e;else return"/"+e.replace(/\\/g,"/")}()+"/"}},function(){function e(){try{throw new Error}catch(t){var e=t.stack,r=new RegExp("^ *at [^(]*\\((.*):[0-9]*:[0-9]*\\)$","mg"),l=null;do{var n=r.exec(e);if(null!=n)l=n}while(null!=n);return l[1]}}var r=null;self.document={get currentScript(){if(null==r)r={src:e()};return r}}}(),self.dartDeferredLibraryLoader=function(e,r,l){try{load(e),r()}catch(e){l(e)}}}
\ No newline at end of file
diff --git a/package.json b/package.json
new file mode 100644
index 0000000..2807441
--- /dev/null
+++ b/package.json
@@ -0,0 +1,8 @@
+{
+  "dependencies": {
+    "terser": "^4.2.1"
+  },
+  "scripts": {
+    "minify": "node tool/minify.js"
+  }
+}
diff --git a/tool/minify.dart b/tool/minify.dart
deleted file mode 100644
index 3de1da9..0000000
--- a/tool/minify.dart
+++ /dev/null
@@ -1,33 +0,0 @@
-import 'dart:io';
-import 'dart:isolate';
-
-import 'package:http/http.dart' as http;
-
-main() async {
-  var packageUrl = Uri.parse('package:node_preamble/');
-  var lib = (await Isolate.resolvePackageUri(packageUrl)).toFilePath();
-
-  var preamble = new File('$lib/preamble.js').readAsStringSync();
-
-  var response = await http.post("https://javascript-minifier.com/raw",
-      body: {"input": preamble});
-  new File("$lib/preamble.min.js").writeAsStringSync(response.body);
-
-  new File("$lib/preamble.dart").writeAsStringSync("""
-library node_preamble;
-
-final _minified = r\"""${response.body}\""";
-
-final _normal = r\"""
-$preamble\""";
-
-/// Returns the text of the preamble.
-///
-/// If [minified] is true, returns the minified version rather than the
-/// human-readable version.
-String getPreamble({bool minified: false, List<String> additionalGlobals: const []}) =>
-    (minified ? _minified : _normal) +
-    (additionalGlobals == null ? "" :
-        additionalGlobals.map((global) => "self.\$global=\$global;").join());
-""");
-}
diff --git a/tool/minify.js b/tool/minify.js
new file mode 100644
index 0000000..dd91596
--- /dev/null
+++ b/tool/minify.js
@@ -0,0 +1,43 @@
+const fs = require("fs");
+const path = require("path");
+
+const Terser = require("terser");
+
+const LIB_DIR = path.join(__dirname, "..", "lib");
+
+const PATH = path.join(LIB_DIR, "preamble.js");
+
+const MIN_PATH = path.join(LIB_DIR, "preamble.min.js");
+const DART_PATH = path.join(LIB_DIR, "preamble.dart");
+
+const preamble = fs.readFileSync(PATH).toString();
+
+const { code: minified, error } = Terser.minify(preamble, {
+  // Needed for Webpack require override.
+  compress: {
+    conditionals: false
+  }
+});
+
+if (error) {
+  throw error;
+}
+
+fs.writeFileSync(MIN_PATH, minified);
+
+fs.writeFileSync(DART_PATH, `library node_preamble;
+
+final _minified = r\"""${minified}\""";
+
+final _normal = r\"""
+${preamble}\""";
+
+/// Returns the text of the preamble.
+///
+/// If [minified] is true, returns the minified version rather than the
+/// human-readable version.
+String getPreamble({bool minified: false, List<String> additionalGlobals: const []}) =>
+    (minified ? _minified : _normal) +
+    (additionalGlobals == null ? "" :
+        additionalGlobals.map((global) => "self.\$global=\$global;").join());
+`);
\ No newline at end of file
diff --git a/yarn.lock b/yarn.lock
new file mode 100644
index 0000000..fdca61a
--- /dev/null
+++ b/yarn.lock
@@ -0,0 +1,35 @@
+# THIS IS AN AUTOGENERATED FILE. DO NOT EDIT THIS FILE DIRECTLY.
+# yarn lockfile v1
+
+
+buffer-from@^1.0.0:
+  version "1.1.1"
+  resolved "https://registry.yarnpkg.com/buffer-from/-/buffer-from-1.1.1.tgz#32713bc028f75c02fdb710d7c7bcec1f2c6070ef"
+  integrity sha512-MQcXEUbCKtEo7bhqEs6560Hyd4XaovZlO/k9V3hjVUF/zwW7KBVdSK4gIt/bzwS9MbR5qob+F5jusZsb0YQK2A==
+
+commander@^2.20.0:
+  version "2.20.0"
+  resolved "https://registry.yarnpkg.com/commander/-/commander-2.20.0.tgz#d58bb2b5c1ee8f87b0d340027e9e94e222c5a422"
+  integrity sha512-7j2y+40w61zy6YC2iRNpUe/NwhNyoXrYpHMrSunaMG64nRnaf96zO/KMQR4OyN/UnE5KLyEBnKHd4aG3rskjpQ==
+
+source-map-support@~0.5.12:
+  version "0.5.13"
+  resolved "https://registry.yarnpkg.com/source-map-support/-/source-map-support-0.5.13.tgz#31b24a9c2e73c2de85066c0feb7d44767ed52932"
+  integrity sha512-SHSKFHadjVA5oR4PPqhtAVdcBWwRYVd6g6cAXnIbRiIwc2EhPrTuKUBdSLvlEKyIP3GCf89fltvcZiP9MMFA1w==
+  dependencies:
+    buffer-from "^1.0.0"
+    source-map "^0.6.0"
+
+source-map@^0.6.0, source-map@~0.6.1:
+  version "0.6.1"
+  resolved "https://registry.yarnpkg.com/source-map/-/source-map-0.6.1.tgz#74722af32e9614e9c287a8d0bbde48b5e2f1a263"
+  integrity sha512-UjgapumWlbMhkBgzT7Ykc5YXUT46F0iKu8SGXq0bcwP5dz/h0Plj6enJqjz1Zbq2l5WaqYnrVbwWOWMyF3F47g==
+
+terser@^4.2.1:
+  version "4.2.1"
+  resolved "https://registry.yarnpkg.com/terser/-/terser-4.2.1.tgz#1052cfe17576c66e7bc70fcc7119f22b155bdac1"
+  integrity sha512-cGbc5utAcX4a9+2GGVX4DsenG6v0x3glnDi5hx8816X1McEAwPlPgRtXPJzSBsbpILxZ8MQMT0KvArLuE0HP5A==
+  dependencies:
+    commander "^2.20.0"
+    source-map "~0.6.1"
+    source-map-support "~0.5.12"