diff --git a/docs/api.md b/docs/api.md
index ce969b39a..e6e95bd5d 100644
--- a/docs/api.md
+++ b/docs/api.md
@@ -1,5 +1,5 @@
 # API Reference
 
 :::warning 🚧 Under construction
-This documentation does not exist yet.
+This documentation does not exist yet. All APIs are documented with JSDoc, so for now, you can view the documentation in your editor.
 :::
diff --git a/docs/guide/auto-imports.md b/docs/guide/auto-imports.md
index d472e7393..0cb8c74e3 100644
--- a/docs/guide/auto-imports.md
+++ b/docs/guide/auto-imports.md
@@ -13,6 +13,7 @@ Some WXT APIs can be used without importing them:
 - [`browser`](/config.md#browser) from `wxt/browser`, a small wrapper around `webextension-polyfill`
 - [`defineContentScript`](/config.md#defiencontentscript) from `wxt/client`
 - [`defineBackground`](/config.md#definebackgroundscript) from `wxt/client`
+- [`createContentScriptUi`](/config.md#createcontentscriptui) from `wxt/client`
 
 And more. All [`wxt/client`](/config.md#wxtclient) APIs can be used without imports.
 
diff --git a/docs/guide/content-scripts.md b/docs/guide/content-scripts.md
index b14802bb0..b4c0997bb 100644
--- a/docs/guide/content-scripts.md
+++ b/docs/guide/content-scripts.md
@@ -47,6 +47,43 @@ export default defineContentScript({
 
 When defining multiple content scripts, content script entrypoints that have the same set of options will be merged into a single `content_script` item in the manifest.
 
+## Context
+
+Old content scripts are not automatically stopped when an extension updates and reloads. Often, this leads to "Invalidated context" errors in production when a content script from an old version of your extension tries to use a extension API.
+
+WXT provides a utility for managing this process: `ContentScriptContext`. An instance of this class is provided to you automatically inside the `main` function of your content script.
+
+```ts
+export default defineContentScript({
+  // ...
+  main(ctx: ContentScriptContext) {
+    // Add custom listeners for stopping work
+    ctx.onInvalidated(() => {
+      // ...
+    });
+
+    // Stop fetch requests
+    fetch('...url', { signal: ctx.signal });
+
+    // Timeout utilities
+    ctx.setTimeout(() => {
+      // ...
+    }, 5e3);
+    ctx.setInterval(() => {
+      // ...
+    }, 60e3);
+  },
+});
+```
+
+The class extends [`AbortController`](https://developer.mozilla.org/en-US/docs/Web/API/AbortController) and provides other utilities for stopping a content script's logic once it becomes invalidated.
+
+:::tip
+When working with content scripts, **you should always use the `ctx` object to stop any async or future work.**
+
+This prevents old content scripts from interfering with new content scripts, and prevents error messages from the console in production.
+:::
+
 ## CSS
 
 To include CSS with your content script, import the CSS file at the top of your entrypoint.
@@ -66,6 +103,7 @@ import './style.css';
 
 export default defineContentScript({
   matches: ['*://google.com/*', '*://duckduckgo.com/*'],
+
   main(ctx) {
     // ...
   },
@@ -87,39 +125,168 @@ Any styles imported in your content script will be added to that content script'
 }
 ```
 
-## Context
+To disable this behavior, set `cssInjectionMode` to `"manual"` or `"ui"`.
 
-Old content scripts are not automatically stopped when an extension updates and restarts. Often, this leads to "Invalidated context" errors in production when a content script from an old version of your extension tries to use a web extension API. Since it's not connected to the latest version of your extension, the browser decides to throw an error.
+```ts
+export default defineContentScript({
+  matches: ['*://google.com/*', '*://duckduckgo.com/*'],
+  cssInjectionMode: 'manual',
 
-WXT provides a utility for managing this process: `ContentScriptContext`. An instance of this class is provided to you automatically inside the `main` function of your content script.
+  main(ctx) {
+    // ...
+  },
+});
+```
+
+## UI
+
+WXT provides a utility function, `createContentScriptUi` to simplify mounting a UI from a content script. Internally, it uses the `ShadowRoot` API to isolate your CSS from the webpages.
+
+`createContentScriptUi` requires a `ContentScriptContext` so that when the context is invalidated, the UI is automatically removed from the webpage.
+
+:::details When to use `createContentScriptUi`
+You should only use `createContentScriptUi` if you want your UI's styles isolated from the webpages. If you want to create a more "integrated" UI that uses the page's styles, you can just use the regular JS API's to append your UI to the page.
+
+```ts
+const ui = document.createElement('div');
+const anchor = document.querySelector('#anchor-selector');
+anchor.append(ui);
+```
+
+:::
+
+### Usage
+
+To use `createContentScriptUi`, follow these steps:
+
+1. Import your CSS file at the top of your content script
+2. Set `cssInjectionMode: "ui"` inside `defineContentScript`
+3. Call `createContentScriptUi`
+4. Call `ui.mount()` to add the UI to the webpage
+
+Here's a basic example:
 
 ```ts
+// entrypoints/ui.content/index.ts
+import './style.css';
+
 export default defineContentScript({
   // ...
-  main(ctx: ContentScriptContext) {
-    // Add custom listeners for stopping work
-    ctx.onInvalidated(() => {
-      // ...
+  cssInjectionMode: 'ui',
+
+  async main(ctx) {
+    const ui = await createContentScriptUi(ctx, {
+      name: 'example-ui',
+      type: 'inline',
+      anchor: '#some-element',
+      append: 'after',
+      mount(container) {
+        // Mount UI inside `container`...
+      },
     });
 
-    // Stop fetch requests
-    fetch('...url', { signal: ctx.signal });
+    // Yoy must call `mount` to add the UI to the page.
+    ui.mount();
+  },
+});
+```
 
-    // Timeout utilities
-    ctx.setTimeout(() => {
-      // ...
-    }, 5e3);
-    ctx.setInterval(() => {
-      // ...
-    }, 60e3);
+If you're using a frontend framework, you'll also need to include an `onRemoved` callback:
+
+:::code-group
+
+```ts [Vue]
+import { createApp } from 'vue';
+
+createContentScriptUi(ctx, {
+  // ...
+  mount(container) {
+    // Create a new app and mount it inside the container
+    const app = createApp(...);
+    app.mount(container);
+    return app;
+  },
+  onRemove(app) {
+    // When the UI is removed from the DOM, call unmount to stop the app
+    app.unmount();
   },
 });
 ```
 
-The class extends [`AbortController`](https://developer.mozilla.org/en-US/docs/Web/API/AbortController) and provides other utilities for stopping a content script's logic once it becomes invalidated.
+```ts [React]
+import ReactDOM from 'react-dom/client';
 
-:::tip
-When working with content scripts, **you should always use the `ctx` object to stop any async or future work.**
+createContentScriptUi(ctx, {
+  // ...
+  mount(container) {
+    // Create a root using the container and render your app
+    const root = ReactDOM.createRoot(container);
+    root.render(...);
+    return root;
+  },
+  onRemove(root) {
+    // When the UI is removed from the DOM, call unmount to stop the app
+    root.unmount();
+  },
+});
+```
+
+```ts [Svelte]
+import App from './App.svelte';
+
+createContentScriptUi(ctx, {
+  // ...
+  mount(container) {
+    // Mount your app component inside the container
+    return new App({
+      target: container,
+    });
+  },
+  onRemove(app) {
+    // When the UI is removed from the DOM, call $destroy to stop the app
+    app.$destroy();
+  },
+});
+```
+
+```ts [Solid]
+import { render } from 'solid-js/web';
+
+createContentScriptUi(ctx, {
+  // ...
+  mount(container) {
+    // Render your app component into the container
+    return render(() => ..., container)
+  },
+  onRemove(unmount) {
+    // When the UI is removed from the DOM, call unmount to stop the app
+    unmount();
+  },
+});
+```
 
-This prevents old content scripts from interfering with new content scripts, and prevents error messages from the console in production.
 :::
+
+### `anchor`
+
+The anchor dictates where the UI will be mounted.
+
+### `append`
+
+Customize where the UI get's appended to the DOM, relative to the `anchor` element.
+
+### `type`
+
+There are 3 types of UI's you can mount.
+
+- `inline`: Shows up inline based on the `anchor` and `append` options
+- `overlay`: Shows up inline, but styled to be 0px by 0px, with overflow visible. This causes the UI to overlay on top of the webpage's content
+- `modal`: A fullscreen overlay that covers the entire screen, regardless of where it's anchored.
+
+> TODO: Add visualization of the different UI types.
+
+### Overlay `alignment`
+
+Because the overlay UI type results in a 0px by 0px container being added to the webpage, the `alignment` option allows you to configure which corner of your UI is aligned with the 0x0 element.
+
+> TODO: Add visualization of the different alignments.