Incompatibilidades con Chrome

WebExtensions are designed to be compatible with Chrome and Opera extensions: as far as possible, extensions written for those browsers should run on Firefox with minimal changes.

However, Firefox currently has support for only a limited set of the features and APIs supported by Chrome and Opera. We're working on adding more support, but many features are not yet supported, and we may never support some.

This article lists all features and APIs that are fully or partially supported in Firefox. Where a feature is partially supported, we've indicated what the gaps are.

It's safe to assume that features and APIs not listed here at all are not yet supported.

manifest.json features

Fully supported keys

Partially supported keys

background

Firefox does not support the "persistent" property. Background scripts stay loaded all the time.

content_scripts

Firefox does not currently support:

include_globs
exclude_globs
match_about_blank

permissions

Firefox does not yet support the following permissions:

activeTab
background
clipboardRead
clipboardWrite
geolocation
nativeMessaging
unlimitedStorage

Obviously, it also don't yet support permissions for APIs that are themselves not supported.

APIs JavaScript

APIs completamente soportadas

alarmas
Menú contextual
pageAction
- Relative URLs passed to setPopup() are resolved relative to the caller document, rather than to the extension root.

APIs parcialmente soportadas

marcadores

Firefox does not support:
- getRecent()
- search()
- removeTree() (remove also removes non-empty folders)
- onCreated
- onRemoved
- onChanged
- onMoved
- onChildrenReordered
- onImportBegan
- onImportEnded
- BookmarkTreeNodeUnmodifiable
Firefox has special bookmarks like "Recently Bookmarked" or "Recently Visited"

browserAction

Firefox does not support:
- enable() or disable().
Relative URLs passed to setPopup() are resolved relative to the caller document, rather than to the extension root.

cookies

onChanged events might be subtely different
Creating session cookies with set might fail
getAllCookieStores always just returns one default store and no tabs
accessing cookies from private tabs is impossible

extension

Firefox only supports:
- getBackgroundPage()
- getURL()
- inIncognitoContext in content scripts

i18n

En la API JavaScript API, Firefox solo soporta getMessage().
Firefox solo soporta los mensajes predefinidos @@extension_id y @@ui_locale.
Firefox no localiza archivos CSS.
Las cadenas para ser localizadas deben consistir enteramente de __MSG_foo__ con el fin de realizar una sustitución al crearlas.

notifications

The only supported notification options are:
- iconUrl
- title
- message.
The only supported methods are:
- create()
- clear()
- getAll().
The only supported event is onClosed.
Firefox doesn't provide byUser data.

runtime

Firefox only supports:
- onStartup()
- getManifest()
- getURL()
- id
- sendMessage()
- onMessage
- onConnect

storage

The only storage area Firefox supports is local.
Firefox does not support getBytesInUse() or clear().

tabs

Firefox does not support:
- getCurrent()
- sendRequest()
- getSelected()
- duplicate()
- highlight()
- move()
- detectLanguage()
- captureVisibleTab()
- getZoom()
- setZoom()
- getZoomSettings()
- setZoomSettings()

Firefox treats highlighted and active as the same since Firefox cannot select multiple tabs.

Firefox doesn't yet support the callback argument to executeScript().

webNavigation

Firefox does not support:
- getFrame()
- getAllFrames()
- onCreatedNavigationTarget
- onHistoryStateUpdated
- transition types and qualifiers
- Filtering

onReferenceFragmentUpdated also triggers for pushState.

webRequest

Firefox does not support:
- handlerBehaviorChanged()
- onAuthRequired
- onBeforeRedirect
- onErrorOccurred
Requests can be:
- canceled only in onBeforeRequest
- modified/redirected only in onBeforeSendHeaders
Responses can be modified only in onHeadersReceived.
Filtering by windowId and tabId is not supported.
The "requestBody" instruction in opt_extraInfoSpec is not supported.
Redirection is not allowed in onBeforeRequest or onHeadersReceived, but is allowed in onBeforeSendHeaders.
requestId is not included in the argument passed to the listener.

windows

onFocusChanged will trigger multiple times for a given focus change.
create() does not support the focused, type, or state options.
update() only supports the focused option.

Planned APIs

We don't yet support the following APIs, but plan to, soon:

CSS

Localized String Interpolation

We currently do not support interpolation of localized strings __MSG_ tokens in extension CSS files: bug 1209184.

Relative URLs

We resolve URLs in injected CSS files relative to the CSS file itself, rather than to the page it's injected into.

Miscellaneous incompatibilities

Chrome allows any optional arguments to be omitted, even if followed by other arguments. Firefox currently supports this only under specific circumetances. We recommend only omitting optional arguments at the end of the arguments list, and using null for all other cases.
Firefox currently does not allow the let or const statement in ordinary web pages or Web Extensions. While it is possible to enable support for Firefox's variant of the statement using a special <script> tag, this is not recommended. Instead, if your extension code uses let or const statements, we recommend that you transpile them using Babel until support is turned on globally.