@@ -92,10 +92,12 @@ module.exports = {
         "bin/*"
       ],
       rules: {
-        // Node's support for ESM is still not great, but this rule is likely
-        // to become activated once compatibility doesn't suck anymore.
+        // We are testing both ESM and UMD, so don't limit us.
         "@typescript-eslint/no-var-requires": "off",
 
+        // This rule does not behave well in JS files.
+        "@typescript-eslint/explicit-module-boundary-types": "off",
+
         // Enforcing to remove function parameters on stubs makes code less
         // maintainable, so we instead allow unused function parameters.
         "no-unused-vars": [
 
@@ -33,6 +33,7 @@ jobs:
         node node_modules/semantic-release/bin/semantic-release.js --unstable
         cd lib/loader
         if [ $(node -pe "require('./package.json').version") != "0.0.0" ]; then
+          npm run build
           npm config set "//registry.npmjs.org/:_authToken=${NPM_TOKEN}"
           npm publish --access public
         fi
 
@@ -53,21 +53,11 @@ jobs:
     - name: Check sources
       run: npm run check
     - name: Test sources
-      run: |
-        if [[ `node bin/asc --version` != *"-dev" ]]; then
-          echo "ERROR: Not testing sources"
-          exit 1
-        fi
-        npm test
+      run: npm test
     - name: Build distribution files
       run: npm run build
     - name: Test distribution
-      run: |
-        if [[ `node bin/asc --version` == *"-dev" ]]; then
-          echo "ERROR: Not testing distribution"
-          exit 1
-        fi
-        npm test
+      run: npm test
     - name: Test browser build
       run: node tests/browser-asc
   test-windows:
 
@@ -22,7 +22,7 @@
  *
  * Uses the low-level API exported from src/index.ts so it works with the compiler compiled to
  * JavaScript as well as the compiler compiled to WebAssembly (eventually). Runs the sources
- * directly through ts-node if distribution files are not present (indicated by a `-dev` version).
+ * directly through ts-node if distribution files are not present.
  *
  * Can also be packaged as a bundle suitable for in-browser use with the standard library injected
  * in the build step. See dist/asc.js for the bundle and webpack.config.js for building details.
@@ -75,23 +75,23 @@ if (process.removeAllListeners) process.removeAllListeners("uncaughtException");
 
 // Use distribution files if present, otherwise run the sources directly.
 var assemblyscript;
-var isDev = false;
 (function loadAssemblyScript() {
   try {
+    // note that this case will always trigger in recent node.js versions for typical installs
+    // see: https://nodejs.org/api/packages.html#packages_self_referencing_a_package_using_its_name
     assemblyscript = require("assemblyscript");
   } catch (e) {
-    try { // `asc` on the command line
+    try { // `asc` on the command line (unnecessary in recent node)
       assemblyscript = dynrequire("../dist/assemblyscript.js");
     } catch (e) {
-      try { // `asc` on the command line without dist files
+      try { // `asc` on the command line without dist files (unnecessary in recent node)
         dynrequire("ts-node").register({
           project: path.join(__dirname, "..", "src", "tsconfig.json"),
           skipIgnore: true,
           compilerOptions: { target: "ES2016" }
         });
         dynrequire("../src/glue/js");
         assemblyscript = dynrequire("../src");
-        isDev = true;
       } catch (e_ts) {
         try { // `require("dist/asc.js")` in explicit browser tests
           assemblyscript = dynrequire("./assemblyscript");
@@ -106,9 +106,6 @@ var isDev = false;
 /** Whether this is a webpack bundle or not. */
 exports.isBundle = typeof BUNDLE_VERSION === "string";
 
-/** Whether asc runs the sources directly or not. */
-exports.isDev = isDev;
-
 /** AssemblyScript version. */
 exports.version = exports.isBundle ? BUNDLE_VERSION : dynrequire("../package.json").version;
 
@@ -241,7 +238,7 @@ exports.main = function main(argv, options, callback) {
 
   // Just print the version if requested
   if (opts.version) {
-    stdout.write("Version " + exports.version + (isDev ? "-dev" : "") + EOL);
+    stdout.write("Version " + exports.version + EOL);
     return callback(null);
   }
 
 
@@ -1,5 +1,3 @@
-"use strict";
-
 // Runtime header offsets
 const ID_OFFSET = -8;
 const SIZE_OFFSET = -4;
@@ -297,7 +295,7 @@ function isModule(src) {
 }
 
 /** Asynchronously instantiates an AssemblyScript module from anything that can be instantiated. */
-async function instantiate(source, imports = {}) {
+export async function instantiate(source, imports = {}) {
   if (isResponse(source = await source)) return instantiateStreaming(source, imports);
   const module = isModule(source) ? source : await WebAssembly.compile(source);
   const extended = preInstantiate(imports);
@@ -306,21 +304,17 @@ async function instantiate(source, imports = {}) {
   return { module, instance, exports };
 }
 
-exports.instantiate = instantiate;
-
 /** Synchronously instantiates an AssemblyScript module from a WebAssembly.Module or binary buffer. */
-function instantiateSync(source, imports = {}) {
+export function instantiateSync(source, imports = {}) {
   const module = isModule(source) ? source : new WebAssembly.Module(source);
   const extended = preInstantiate(imports);
   const instance = new WebAssembly.Instance(module, imports);
   const exports = postInstantiate(extended, instance);
   return { module, instance, exports };
 }
 
-exports.instantiateSync = instantiateSync;
-
 /** Asynchronously instantiates an AssemblyScript module from a response, i.e. as obtained by `fetch`. */
-async function instantiateStreaming(source, imports = {}) {
+export async function instantiateStreaming(source, imports = {}) {
   if (!WebAssembly.instantiateStreaming) {
     return instantiate(
       isResponse(source = await source)
@@ -335,10 +329,8 @@ async function instantiateStreaming(source, imports = {}) {
   return { ...result, exports };
 }
 
-exports.instantiateStreaming = instantiateStreaming;
-
 /** Demangles an AssemblyScript module's exports to a friendly object structure. */
-function demangle(exports, extendedExports = {}) {
+export function demangle(exports, extendedExports = {}) {
   extendedExports = Object.create(extendedExports);
   const setArgumentsLength = exports["__argumentsLength"]
     ? length => { exports["__argumentsLength"].value = length; }
@@ -420,4 +412,9 @@ function demangle(exports, extendedExports = {}) {
   return extendedExports;
 }
 
-exports.demangle = demangle;
+export default {
+  instantiate,
+  instantiateSync,
+  instantiateStreaming,
+  demangle
+};
@@ -21,18 +21,27 @@
   "bugs": {
     "url": "https://github.com/AssemblyScript/assemblyscript/issues"
   },
+  "type": "module",
   "main": "index.js",
   "types": "index.d.ts",
+  "exports": {
+    "import": "./index.js",
+    "require": "./umd/index.js"
+  },
   "scripts": {
     "asbuild": "npm run asbuild:default && npm run asbuild:legacy",
     "asbuild:default": "node ../../bin/asc tests/assembly/index.ts -b tests/build/default.wasm",
     "asbuild:legacy": "node ../../bin/asc tests/assembly/index.ts --disable mutable-globals -b tests/build/legacy.wasm",
-    "test": "node tests"
+    "build": "npx esm2umd loader index.js > umd/index.js",
+    "test": "node tests && node tests/umd"
   },
   "files": [
     "index.d.ts",
     "index.js",
     "package.json",
+    "umd/index.d.ts",
+    "umd/index.js",
+    "umd/package.json",
     "README.md"
   ]
 }
@@ -1,8 +1,12 @@
-var fs = require("fs");
-var assert = require("assert");
-var inspect = require("util").inspect;
-
-var loader = require("..");
+import fs from "fs";
+import assert from "assert";
+import { inspect } from "util";
+import loader from "../index.js";
+import { dirname } from "path";
+import { fileURLToPath } from "url";
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = dirname(__filename);
 
 test("default.wasm");
 test("legacy.wasm");
 
@@ -0,0 +1,4 @@
+const assert = require("assert");
+const loader = require("../../umd");
+
+assert(typeof loader.instantiate === "function");
@@ -0,0 +1,3 @@
+{
+  "type": "commonjs"
+}
@@ -0,0 +1 @@
+export * from "..";