diff --git a/.eslintignore b/.eslintignore
index 849ddff..26a203e 100644
--- a/.eslintignore
+++ b/.eslintignore
@@ -1 +1,2 @@
 dist/
+add_esm_import_extensions.mjs
\ No newline at end of file
diff --git a/.nvmrc b/.nvmrc
new file mode 100644
index 0000000..e0325e5
--- /dev/null
+++ b/.nvmrc
@@ -0,0 +1 @@
+v16.17.1
diff --git a/History.md b/History.md
index ab51baf..9bea7a3 100644
--- a/History.md
+++ b/History.md
@@ -1,3 +1,14 @@
+4.1.0 / 2023-01-25
+==================
+
+ * Support ESM Modules
+
+4.0.2 / 2023-01-12
+==================
+
+ * #71 : @import does not work if url contains ';'
+ * #77 : Regression in selector parsing: Attribute selectors not parsed correctly
+
 4.0.1 / 2022-08-03
 ==================
 
diff --git a/Readme.md b/Readme.md
index 2eef21a..4538720 100644
--- a/Readme.md
+++ b/Readme.md
@@ -6,19 +6,19 @@ CSS parser / stringifier.
 
 ## Installation
 
-    $ npm install css
+    $ npm install @adobe/css-tools
 
 ## Usage
 
 ```js
-var css = require('css');
-var obj = css.parse('body { font-size: 12px; }', options);
-css.stringify(obj, options);
+import { parse, stringify } from '@adobe/css-tools'
+let obj = parse('body { font-size: 12px; }', options);
+let css = stringify(obj, options);
 ```
 
 ## API
 
-### css.parse(code, [options])
+### parse(code, [options])
 
 Accepts a CSS string and returns an AST `object`.
 
@@ -28,7 +28,7 @@ Accepts a CSS string and returns an AST `object`.
 - source: the path to the file containing `css`. Makes errors and source
   maps more helpful, by letting them know where code comes from.
 
-### css.stringify(object, [options])
+### stringify(object, [options])
 
 Accepts an AST `object` (as `css.parse` produces) and returns a CSS string.
 
@@ -40,9 +40,9 @@ Accepts an AST `object` (as `css.parse` produces) and returns a CSS string.
 ### Example
 
 ```js
-var ast = css.parse('body { font-size: 12px; }', { source: 'source.css' });
+var ast = parse('body { font-size: 12px; }', { source: 'source.css' });
 
-var css = css.stringify(ast);
+var css = stringify(ast);
 ```
 
 ### Errors
diff --git a/add_esm_import_extensions.mjs b/add_esm_import_extensions.mjs
new file mode 100644
index 0000000..0b37be5
--- /dev/null
+++ b/add_esm_import_extensions.mjs
@@ -0,0 +1,105 @@
+import * as fs from 'fs';
+import * as path from 'path';
+
+// https://gist.github.com/lovasoa/8691344
+async function* walk(dir) {
+  for await (const d of await fs.promises.opendir(dir)) {
+    const entry = path.join(dir, d.name);
+    if (d.isDirectory()) {
+      yield* walk(entry);
+    } else if (d.isFile()) {
+      yield entry;
+    }
+  }
+}
+
+function resolveImportPath(sourceFile, importPath, options) {
+  const sourceFileAbs = path.resolve(process.cwd(), sourceFile);
+  const root = path.dirname(sourceFileAbs);
+  const {moduleFilter = defaultModuleFilter} = options;
+
+  if (moduleFilter(importPath)) {
+    const importPathAbs = path.resolve(root, importPath);
+    const possiblePath = [
+      path.resolve(importPathAbs, './index.ts'),
+      path.resolve(importPathAbs, './index.js'),
+      importPathAbs + '.ts',
+      importPathAbs + '.js',
+    ];
+
+    if (possiblePath.length) {
+      for (let i = 0; i < possiblePath.length; i++) {
+        const entry = possiblePath[i];
+        if (fs.existsSync(entry)) {
+          const resolved = path.relative(root, entry.replace(/\.ts$/, '.js'));
+
+          if (!resolved.startsWith('.')) {
+            return './' + resolved;
+          }
+
+          return resolved;
+        }
+      }
+    }
+  }
+
+  return null;
+}
+
+function replace(filePath, outFilePath, options) {
+  const code = fs.readFileSync(filePath).toString();
+  const newCode = code.replace(
+    /(import|export) (.+?) from ('[^\n']+'|"[^\n"]+");/gs,
+    (found, action, imported, from) => {
+      const importPath = from.slice(1, -1);
+      const resolvedPath = resolveImportPath(filePath, importPath, options);
+
+      if (resolvedPath) {
+        console.log('\t', importPath, resolvedPath);
+        return `${action} ${imported} from '${resolvedPath.replaceAll(
+          '\\',
+          '/'
+        )}';`;
+      }
+
+      return found;
+    }
+  );
+
+  if (code !== newCode) {
+    fs.writeFileSync(outFilePath, newCode);
+  }
+}
+
+// Then, use it with a simple async for loop
+async function run(srcDir, options = defaultOptions) {
+  const {sourceFileFilter = defaultSourceFileFilter} = options;
+
+  for await (const entry of walk(srcDir)) {
+    if (sourceFileFilter(entry)) {
+      console.log(entry);
+      replace(entry, entry, options);
+    }
+  }
+}
+
+const defaultSourceFileFilter = function (sourceFilePath) {
+  return (
+    /\.(js|ts)$/.test(sourceFilePath) && !/node_modules/.test(sourceFilePath)
+  );
+};
+
+const defaultModuleFilter = function (importedModule) {
+  return (
+    !path.isAbsolute(importedModule) &&
+    !importedModule.startsWith('@') &&
+    !importedModule.endsWith('.js')
+  );
+};
+
+const defaultOptions = {
+  sourceFileFilter: defaultSourceFileFilter,
+  moduleFilter: defaultModuleFilter,
+};
+
+run('./dist/esm', defaultOptions);
diff --git a/package.json b/package.json
index 2d10832..4d8aad1 100644
--- a/package.json
+++ b/package.json
@@ -1,9 +1,13 @@
 {
   "name": "@adobe/css-tools",
-  "version": "4.0.2",
+  "version": "4.1.0",
   "description": "CSS parser / stringifier",
   "main": "dist/umd/cssTools.js",
   "module": "dist/cjs/cssTools.js",
+  "exports": {
+    "import": "./dist/esm/index.js",
+    "require": "./dist/cjs/cssTools.js"
+  },
   "types": "dist/cjs/index.d.ts",
   "files": [
     "dist",
@@ -30,8 +34,9 @@
     "test": "jest",
     "lint": "gts lint",
     "clean": "gts clean",
-    "build": "npm run compile",
-    "compile": "NODE_ENV=prod webpack --mode production",
+    "build": "npm run compile && npm run buildesm",
+    "buildesm": "tsc --project tsconfig.esm.json && node ./add_esm_import_extensions.mjs",
+    "compile": "set NODE_ENV=prod & webpack --mode production",
     "fix": "gts fix",
     "prepare": "npm run build",
     "pretest": "npm run build",
diff --git a/tsconfig.esm.json b/tsconfig.esm.json
new file mode 100644
index 0000000..f387b59
--- /dev/null
+++ b/tsconfig.esm.json
@@ -0,0 +1,12 @@
+{
+  "compilerOptions": {
+    "target": "ES2022",
+    "module": "ES2022",
+    "moduleResolution": "node",
+    "rootDir": "src",
+    "outDir": "dist/esm",
+  },
+  "include": [
+    "src/**/*.ts"
+  ]
+}