diff --git a/.github/workflows/prod-test.yml b/.github/workflows/prod-test.yml
index 8e4a4b014..2c328da35 100644
--- a/.github/workflows/prod-test.yml
+++ b/.github/workflows/prod-test.yml
@@ -145,7 +145,7 @@ jobs:
         working-directory: dist/prettier
         run: node bin/prettier.cjs --debug-benchmark package.json 2>&1 >/dev/null | grep "Latency avg" || exit 1
 
-  browser-test:
+  browser:
     timeout-minutes: 15
     strategy:
       fail-fast: false
@@ -191,8 +191,15 @@ jobs:
           name: dist
           path: dist
 
-      - name: Run Tests
-        run: yarn test:production-browser
+      - name: Run Tests (ESM)
+        env:
+          TEST_BUNDLE_FORMAT: esm
+        run: yarn test:production:browser
+
+      - name: Run Tests (UMD)
+        env:
+          TEST_BUNDLE_FORMAT: umd
+        run: yarn test:production:browser
 
   cli:
     name: CLI
diff --git a/package.json b/package.json
index 7de727987..7808baec3 100644
--- a/package.json
+++ b/package.json
@@ -191,9 +191,11 @@
     "test:production-node14": "cross-env NODE_ENV=production yarn test:node14",
     "test:production-standalone": "cross-env TEST_STANDALONE=1 yarn test:production",
     "test:production-standalone-node14": "cross-env TEST_STANDALONE=1 yarn test:production-node14",
-    "test:production-browser": "cross-env  NODE_ENV=production TEST_RUNTIME=browser yarn test",
-    "test:production-browser:chrome": "cross-env TEST_RUNTIME_BROWSER=chrome yarn test:production-browser",
-    "test:production-browser:firefox": "cross-env TEST_RUNTIME_BROWSER=firefox yarn test:production-browser",
+    "test:production:browser": "cross-env TEST_RUNTIME=browser yarn test:production",
+    "test:production:browser:chrome": "cross-env TEST_RUNTIME_BROWSER=chrome yarn test:production:browser",
+    "test:production:browser:firefox": "cross-env TEST_RUNTIME_BROWSER=firefox yarn test:production:browser",
+    "test:production:browser:chrome:umd": "cross-env TEST_BUNDLE_FORMAT=umd yarn test:production:browser:chrome",
+    "test:production:browser:firefox:umd": "cross-env TEST_BUNDLE_FORMAT=umd yarn test:production:browser:firefox",
     "test:production-lint": "eslint dist --config=./scripts/production-eslint-config.js --quiet --format friendly",
     "perf": "yarn && yarn build && cross-env NODE_ENV=production node ./dist/prettier/bin/prettier.cjs",
     "perf:inspect": "yarn && yarn build && cross-env NODE_ENV=production node --inspect-brk ./dist/prettier/bin/prettier.cjs",
diff --git a/src/standalone.js b/src/standalone.js
index e5ed71f06..12401b443 100644
--- a/src/standalone.js
+++ b/src/standalone.js
@@ -6,7 +6,6 @@ function withPlugins(
   optionsArgumentIndex = 1, // Usually `options` is the 2nd argument
 ) {
   // Returns Promises to consistent with functions in `index.js`
-  // eslint-disable-next-line require-await
   return async (...args) => {
     const options = args[optionsArgumentIndex] ?? {};
     const plugins = options.plugins ?? [];
@@ -16,7 +15,7 @@ function withPlugins(
       plugins: Array.isArray(plugins) ? plugins : Object.values(plugins),
     };
 
-    return fn(...args);
+    return await fn(...args);
   };
 }
 
diff --git a/tests/config/browser/get-browser-prettier.js b/tests/config/browser/get-browser-prettier.js
index 85bf3a47e..141e8286f 100644
--- a/tests/config/browser/get-browser-prettier.js
+++ b/tests/config/browser/get-browser-prettier.js
@@ -3,7 +3,10 @@ import { startServer } from "./server.js";
 import { requestFromNode } from "./utilities.js";
 
 async function getBrowserPrettier() {
+  /** @type {"chrome" | "firefox"} */
   const browserName = process.env.TEST_RUNTIME_BROWSER ?? "chrome";
+  /** @type {"esm" | "umd"} */
+  const prettierBundleFormat = process.env.TEST_BUNDLE_FORMAT ?? "esm";
   const browser = await launchBrowser({ browser: browserName });
 
   process.once("exit", async () => {
@@ -16,14 +19,14 @@ async function getBrowserPrettier() {
   });
 
   const page = await browser.newPage();
-  await page.goto(server.url + "/esm.html");
+  await page.goto(server.url);
 
   const proxyFunction = (accessPath, optionsIndex = 1) =>
     requestFromNode(
       (...arguments_) =>
         page.evaluate(
-          ([arguments_, accessPath]) => {
-            const prettier = globalThis.__prettier;
+          ([arguments_, accessPath, prettierBundleFormat]) => {
+            const prettier = globalThis[`__prettier_${prettierBundleFormat}`];
             let function_ = prettier;
             for (const property of accessPath.split(".")) {
               function_ = function_[property];
@@ -31,7 +34,7 @@ async function getBrowserPrettier() {
 
             return function_(...arguments_);
           },
-          [arguments_, accessPath],
+          [arguments_, accessPath, prettierBundleFormat],
         ),
       {
         browser: browserName,
diff --git a/tests/config/browser/esm.html b/tests/config/browser/index.html
similarity index 69%
rename from tests/config/browser/esm.html
rename to tests/config/browser/index.html
index ad94d922d..506854947 100644
--- a/tests/config/browser/esm.html
+++ b/tests/config/browser/index.html
@@ -6,7 +6,10 @@
     <title>Document</title>
   </head>
   <body>
-    <div>Use <code>__prettier</code> to debug in console.</div>
+    <div>
+      Use <code>__prettier_esm</code> or <code>__prettier_umd</code> to debug in
+      console.
+    </div>
     <script type="module" src="main.js"></script>
   </body>
 </html>
diff --git a/tests/config/browser/main.js b/tests/config/browser/main.js
index 94c775693..44b054809 100644
--- a/tests/config/browser/main.js
+++ b/tests/config/browser/main.js
@@ -1,4 +1,4 @@
-import { responseInBrowser } from "./utilities.js";
+import { ensurePromise, responseInBrowser } from "./utilities.js";
 
 const browser = navigator.userAgent.includes("Firefox/") ? "firefox" : "chrome";
 
@@ -22,50 +22,140 @@ const esmFiles = {
     "plugin-oxc/index.browser.mjs",
   ],
 };
+const umdFiles = {
+  prettier: "prettier/standalone.js",
+  plugins: [
+    "prettier/plugins/angular.js",
+    "prettier/plugins/graphql.js",
+    "prettier/plugins/typescript.js",
+    "prettier/plugins/estree.js",
+    "prettier/plugins/markdown.js",
+    "prettier/plugins/acorn.js",
+    "prettier/plugins/glimmer.js",
+    "prettier/plugins/postcss.js",
+    "prettier/plugins/babel.js",
+    "prettier/plugins/html.js",
+    "prettier/plugins/yaml.js",
+    "prettier/plugins/flow.js",
+    "prettier/plugins/meriyah.js",
+    // These two plugins don't have umd version
+    "plugin-hermes/index.mjs",
+    "plugin-oxc/index.browser.mjs",
+  ],
+};
 
-let prettier;
-let builtinPlugins;
+async function loadScript(url) {
+  const { document } = globalThis;
+  const { head } = document;
+  const script = Object.assign(document.createElement("script"), { src: url });
 
-function proxyFunction(accessPath, optionsIndex = 1) {
-  let function_;
-  return responseInBrowser(
-    async (...arguments_) => {
-      if (!prettier) {
-        [prettier, ...builtinPlugins] = await Promise.all(
-          [esmFiles.prettier, ...esmFiles.plugins].map(
-            (file) => import(`/${file}`),
-          ),
-        );
-      }
+  function on(event, callback) {
+    script.addEventListener(event, callback, { once: true, passive: true });
+  }
 
-      if (!function_) {
-        function_ = prettier;
-        for (const property of accessPath.split(".")) {
-          function_ = function_[property];
-        }
-      }
+  try {
+    await new Promise((resolve, reject) => {
+      on("load", resolve);
 
-      const options = arguments_[optionsIndex] ?? {};
+      on("error", () => {
+        reject(new Error(`Failed to load script '${url}'.`));
+      });
 
-      arguments_[optionsIndex] = {
-        ...options,
-        plugins: [...builtinPlugins, ...(options.plugins || [])],
-      };
-
-      return function_(...arguments_);
-    },
-    {
-      browser,
-      accessPath,
-      optionsIndex,
-    },
-  );
+      head.appendChild(script);
+    });
+  } finally {
+    head.removeChild(script);
+  }
 }
 
-globalThis.__prettier = {
-  formatWithCursor: proxyFunction("formatWithCursor"),
-  getSupportInfo: proxyFunction("getSupportInfo", /* optionsIndex */ 0),
-  __debug: {
-    parse: proxyFunction("__debug.parse"),
-  },
-};
+async function loadEsmPrettier() {
+  const [prettier, ...builtinPlugins] = await Promise.all(
+    [esmFiles.prettier, ...esmFiles.plugins].map((file) => import(`/${file}`)),
+  );
+
+  return { prettier, builtinPlugins };
+}
+
+async function loadUmdPrettier() {
+  const { umdPluginFiles, esmPluginFiles } = Object.groupBy(
+    umdFiles.plugins,
+    (file) => `${file.endsWith(".mjs") ? "esm" : "umd"}PluginFiles`,
+  );
+
+  const [, esmPlugins] = await Promise.all([
+    Promise.all(
+      [umdFiles.prettier, ...umdPluginFiles].map((file) =>
+        loadScript(`/${file}`),
+      ),
+    ),
+    Promise.all(esmPluginFiles.map((file) => import(`/${file}`))),
+  ]);
+
+  const { prettier } = globalThis;
+  const builtinPlugins = [
+    ...Object.values(globalThis.prettierPlugins),
+    ...esmPlugins,
+  ];
+  delete globalThis.prettier;
+  delete globalThis.prettierPlugins;
+  return { prettier, builtinPlugins };
+}
+
+/**
+@param {"esm" | "umd"} prettierBundleFormat
+*/
+function createPrettier(prettierBundleFormat) {
+  let cache;
+  function loadPrettier() {
+    if (!cache) {
+      cache =
+        prettierBundleFormat === "esm" ? loadEsmPrettier() : loadUmdPrettier();
+    }
+
+    return cache;
+  }
+
+  const functions = new Map();
+
+  function proxyFunction(accessPath, optionsIndex = 1) {
+    let function_;
+    return responseInBrowser(
+      async (...arguments_) => {
+        const { prettier, builtinPlugins } = await loadPrettier();
+
+        if (!functions.has(accessPath)) {
+          function_ = prettier;
+          for (const property of accessPath.split(".")) {
+            function_ = function_[property];
+          }
+          functions.set(accessPath, function_);
+        }
+
+        const options = arguments_[optionsIndex] ?? {};
+
+        arguments_[optionsIndex] = {
+          ...options,
+          plugins: [...builtinPlugins, ...(options.plugins || [])],
+        };
+
+        return ensurePromise(function_(...arguments_));
+      },
+      {
+        browser,
+        accessPath,
+        optionsIndex,
+      },
+    );
+  }
+
+  return {
+    formatWithCursor: proxyFunction("formatWithCursor"),
+    getSupportInfo: proxyFunction("getSupportInfo", /* optionsIndex */ 0),
+    __debug: {
+      parse: proxyFunction("__debug.parse"),
+    },
+  };
+}
+
+globalThis.__prettier_esm = createPrettier("esm");
+globalThis.__prettier_umd = createPrettier("umd");
diff --git a/tests/config/browser/server.js b/tests/config/browser/server.js
index 0abaeec29..27e4fcd55 100644
--- a/tests/config/browser/server.js
+++ b/tests/config/browser/server.js
@@ -9,7 +9,7 @@ async function getContent(url) {
   assert.ok(url.startsWith("/"));
   url = url.slice(1);
 
-  if (url === "esm.html" || url === "main.js" || url === "utilities.js") {
+  if (url === "index.html" || url === "main.js" || url === "utilities.js") {
     return await fs.readFile(new URL(url, import.meta.url), "utf8");
   }
 
@@ -29,7 +29,7 @@ async function startServer({ silent = false, port: preferredPort } = {}) {
     }
 
     if (url === "/") {
-      url = "/esm.html";
+      url = "/index.html";
     }
 
     // Only allow `.mjs`,  `.js` and `.html`
diff --git a/tests/config/browser/utilities.js b/tests/config/browser/utilities.js
index 9cdddb83c..bad4a70b2 100644
--- a/tests/config/browser/utilities.js
+++ b/tests/config/browser/utilities.js
@@ -157,4 +157,12 @@ function serializeValue(value) {
   return value;
 }
 
-export { requestFromNode, responseInBrowser };
+const ensurePromise = (value) => {
+  if (!(value instanceof Promise)) {
+    throw new TypeError("Expected value to be a 'Promise'.");
+  }
+
+  return value;
+};
+
+export { ensurePromise, requestFromNode, responseInBrowser };