Index: extensions/docs/extension_and_app_types.md |
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+# Extension and App Types |
+ |
+Generally, browser extensions cut across websites and web apps, while apps |
+provide more isolated functionality. |
+ |
+[TOC] |
+ |
+![Summary of extension types showing browser extensions, packaged/platform apps, |
+and hosted/bookmark apps](extension_types.png) |
+ |
+## Browser extensions |
+ |
+Browser extensions often provide an interactive toolbar icon, but can also run |
+without any UI. They may interact with the browser or tab contents, and can |
+request more extensive permissions than apps. |
+ |
+## Apps |
+ |
+### Platform app |
+ |
+Platform apps (*v2 packaged apps*) are standalone applications that mostly run |
+independently of the browser. Their windows look and feel like native |
+applications but simply host the app's pages. |
+ |
+Most apps, like Calculator and the Files app, create their window(s) and |
+initialize a UI in response to Chrome's `chrome.app.runtime.onLaunched` event. |
+Some apps don't show a window but work in the background instead. Platform apps |
+can connect to more device types than browser extensions have access to. |
+ |
+Platform apps are deprecated on non-Chrome OS platforms. |
+ |
+### Packaged app (legacy) |
+ |
+[Legacy (v1) packaged apps](https://developer.chrome.com/extensions/apps) |
+combined the appearance of a [hosted app](#Hosted-app) -- a windowed wrapper |
+around a website -- with the power of extension APIs. With the launch of |
+platform apps and the app-specific APIs, legacy packaged apps are deprecated. |
+ |
+### Hosted app |
+ |
+A [hosted app](https://developer.chrome.com/webstore/hosted_apps) is mostly |
+metadata: a web URL to launch, a list of associated URLs, and a list of HTML5 |
+permissions. Chrome ask for these permissions during the app's installation, |
+allowing the associated URL to bypass the normal Chrome permission prompts for |
+HTML5 features. |
+ |
+### Bookmark app |
+ |
+A bookmark app is a simplified hosted app that Chrome creates on demand. When |
+the user taps "Add to desktop" (or "Add to shelf" on Chrome OS) in the Chrome |
+menu, Chrome creates a barebones app whose manifest specifies the current tab's |
+URL. A shortcut to this URL appears in chrome://apps using the site's favicon. |
+ |
+Chrome then creates a desktop shortcut that will open a browser window with |
+flags that specify the app and profile. Activating the icon launches the |
+"bookmarked" URL in a tab or a window. |
+ |
+## Manifest |
+ |
+A particular manifest key in an extension's `manifest.json` file determines what |
+kind of extension it is: |
+ |
+* Platform app: `app.background.page` and/or `app.background.scripts` |
+* Legacy packaged app: `app.launch.local_path` |
+* Hosted app: `app.launch.web_url` |
+* Browser extension: none of the above |
+ |
+## Notes |
+ |
+`Extension` is the class type for all extensions and apps, so technically |
+speaking, an app *is-an* `Extension`. The word "extension" usually refers only |
+to non-app extensions, a.k.a. *browser extensions*. |
+ |
+## See also |
+ |
+* [`Manifest::Type` declaration](https://cs.chromium.org/chromium/src/extensions/common/manifest.h?gs=cpp%253Aextensions%253A%253Aclass-Manifest%253A%253Aenum-Type%2540chromium%252F..%252F..%252Fextensions%252Fcommon%252Fmanifest.h%257Cdef&gsn=Type&ct=xref_usages) |
+* Extensions (3rd-party developer documentation) |
+ * [Extension APIs](https://developer.chrome.com/extensions/api_index) |
+ * [Extension manifest file format]( |
+ https://developer.chrome.com/extensions/manifest) |
+* Apps (3rd-party developer documentation) |
+ * [Platform app APIs](https://developer.chrome.com/apps/api_index) |
+ * [Platform app manifest file format]( |
+ https://developer.chrome.com/apps/manifest) |
+ * [Choosing an app type](https://developer.chrome.com/webstore/choosing) |
+ * Ancient article introducing the [motivation for apps (outdated)]( |
+ https://developer.chrome.com/webstore/apps_vs_extensions) |