| # Extension and App Types |
| |
| Generally, browser extensions cut across websites and web apps, while apps |
| provide more isolated functionality. |
| |
| [TOC] |
| |
|  |
| |
| ## 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) |
