diff --git a/README.md b/README.md
index 847c4f6..5920b9a 100644
--- a/README.md
+++ b/README.md
@@ -59,9 +59,18 @@ end
 
 ## npm package
 
-This repo also publishes `@bikeindex/time-localizer`, an npm package for localizing time elements in the browser. Luxon is bundled into the published package, so consumers don't need to install it separately.
+This repo also publishes `@bikeindex/time-localizer`, an npm package for localizing time elements in the browser. It ships two builds of the same source:
 
-To publish a new version: update the version in `package.json`, then run `npm publish` from the repo root (requires npm login with access to the `@bikeindex` scope). The `prepublishOnly` script automatically builds `dist/index.js` before publishing.
+| Build | Luxon | Use when |
+| --- | --- | --- |
+| `dist/index.js` (default) | external — install it yourself | You have a bundler. Luxon stays deduped with your own copy, so `Settings.defaultLocale`, `Settings.now` etc. apply to both. |
+| `dist/index.bundle.js` | bundled in | You have no bundler (e.g. importmap-rails). One request, nothing to resolve. |
+
+Import the default as `@bikeindex/time-localizer` and the standalone as `@bikeindex/time-localizer/bundle`, or reference either file path directly over a CDN.
+
+Don't use the bundled build alongside your own Luxon: you'd ship two copies, and because Luxon's `Settings` are module-scoped, your global config would silently apply to only one of them.
+
+To publish a new version: update the version in `package.json`, then run `npm publish` from the repo root (requires npm login with access to the `@bikeindex` scope). The `prepublishOnly` script builds both artifacts before publishing.
 
 ## Releasing
 
diff --git a/package-lock.json b/package-lock.json
index f09631a..e59c4b6 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "@bikeindex/time-localizer",
-  "version": "0.3.0",
+  "version": "0.4.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "@bikeindex/time-localizer",
-      "version": "0.3.0",
+      "version": "0.4.0",
       "license": "MIT",
       "devDependencies": {
         "esbuild": "^0.28.0",
diff --git a/package.json b/package.json
index 76871b2..7bb5c49 100644
--- a/package.json
+++ b/package.json
@@ -1,17 +1,21 @@
 {
   "name": "@bikeindex/time-localizer",
-  "version": "0.3.0",
+  "version": "0.4.0",
   "description": "Localizes time elements to the user's timezone using Luxon",
   "type": "module",
   "main": "dist/index.js",
   "exports": {
-    ".": "./dist/index.js"
+    ".": "./dist/index.js",
+    "./bundle": "./dist/index.bundle.js"
   },
   "files": [
-    "dist/index.js"
+    "dist/index.js",
+    "dist/index.bundle.js"
   ],
   "scripts": {
-    "build": "esbuild index.js --bundle --format=esm --minify --external:luxon --outfile=dist/index.js",
+    "build": "npm run build:esm && npm run build:bundle",
+    "build:esm": "esbuild index.js --bundle --format=esm --minify --external:luxon --outfile=dist/index.js",
+    "build:bundle": "esbuild index.js --bundle --format=esm --minify --outfile=dist/index.bundle.js",
     "prepublishOnly": "npm run build",
     "test": "vitest run"
   },