Are we WebExtensions yet?

Yes, I think we are.

Mozilla documentation on WebExtensions, see also the wiki page. Note: this page is generated from the source, but in cases of discrepancy please rely on MDN more than these docs.

Chrome documentation on WebExtensions.

§ APIs

Filters: desktop onlyandroid onlycomplete onlypartial onlycomplete and partial onlyreset ( APIs)

Legend:

complete
pretty much all the APIs that it makes sense to implement have been done. What remains is undocumented, deprecated or we've thought not worth bothering with (we could be wrong).
partial
is mostly there, there's still some work to do implementing APIs.
android
it should work on Android based on its location in mozilla-central, no guarantees unless MDN says so.
desktop
it should work on Desktop based on its location in mozilla-central, no guarantees unless MDN says so.

§ alarms   desktop  android

Firefox docsFirefox code
§ 0 bugs
§ 5 functions
supported chrome.alarms.create() rank 66
supported chrome.alarms.getAll() rank 195
supported chrome.alarms.clearAll() rank 180
supported chrome.alarms.clear() rank 128
supported chrome.alarms.get() rank 198
§ 1 events
supported chrome.alarms.onAlarm rank 64

§ bookmarks   desktop

Firefox docsFirefox code
§ 10 bugs
1213674: P3 Complete the implementation of chrome.bookmarks
1225916: P3 Allow reading and writing bookmark tags
1251657: P5 bookmarks.search doesn't allow quoted search terms
1276817: P5 Support bookmark keywords
1276819: P5 Support bookmark descriptions
1276821: P5 Support live bookmarks
1291274: -- Consider adding bookmarks API method to get ID of standard/common folders
1293853: P3 Add support for separators to bookmarks API
1316297: P3 Implement remaining bookmarks.onImportBegan and onImportEnded WebExtensions API events
1319530: P3 Implement bookmarks.onChildrenReordered WebExtensions API event
§ 13 functions
supported chrome.bookmarks.search() rank 133
supported chrome.bookmarks.getTree() rank 75
supported chrome.bookmarks.getRecent() rank 205
supported chrome.bookmarks.get() rank 165
supported chrome.bookmarks.create() rank 108
supported chrome.bookmarks.move() rank 177
supported chrome.bookmarks.update() rank 169
supported chrome.bookmarks.remove() rank 120
supported chrome.bookmarks.getChildren() rank 137
not supported internal chrome.bookmarks.export() rank 1008
not supported internal chrome.bookmarks.import() rank 1004
supported chrome.bookmarks.removeTree() rank 163
supported chrome.bookmarks.getSubTree() rank 185
§ 7 events
supported chrome.bookmarks.onRemoved rank 160
not supported chrome.bookmarks.onImportEnded rank 220
supported chrome.bookmarks.onMoved rank 201
not supported chrome.bookmarks.onImportBegan rank 315
supported chrome.bookmarks.onCreated rank 159
supported chrome.bookmarks.onChanged rank 182
not supported chrome.bookmarks.onChildrenReordered rank 215

§ browserAction   desktop

Firefox docsFirefox code
§ 11 bugs
1207591: P5 badge background color - provide 3 recommended colors
1207597: P5 browserAction icon should match appearance of native Firefox toolbar buttons
1207692: P5 provide a highlight state for browserActions
1215632: P4 Unit test to assert that a browser action opens the popup in the parents mode (private vs not-private)
1237377: P2 [meta] WebExtension popup support
1244789: P2 Support richer user interactions in the chrome.browserAction API
1253419: P3 Support menu-button buttons in the browserAction API.
1314674: P5 Background of badge on browserAction button changes to red on entering and remains red on exiting Customize mode
1331126: P2 [tracking] BrowserAction API support for Android WebExtensions
1331742: P2 Add support for browserAction.onClicked
1331746: P2 Add support for browserAction.setIcon
§ 12 functions
supported chrome.browserAction.enable() rank 168
supported chrome.browserAction.setBadgeBackgroundColor() rank 29
supported chrome.browserAction.setBadgeText() rank 13
supported chrome.browserAction.setTitle() rank 34
supported chrome.browserAction.getBadgeText() rank 140
supported chrome.browserAction.setPopup() rank 54
supported chrome.browserAction.disable() rank 155
supported chrome.browserAction.getTitle() rank 253
not supported internal chrome.browserAction.openPopup() rank 440
supported chrome.browserAction.getBadgeBackgroundColor() rank 995
supported chrome.browserAction.getPopup() rank 230
supported chrome.browserAction.setIcon() rank 18
§ 1 events
supported chrome.browserAction.onClicked rank 7

§ browsingData   desktop

Firefox docsFirefox code
§ 5 bugs
1303917: P3 [tracking] Implement browser.browsingData WebExtensions API
1328918: P3 Update test browser_ext_browsingData_serviceWorkers.js after e10s changes land
1329745: -- Requesting WebExtension API to interact with the various LocalStorages Firefox manages
1332613: P3 Update browsingData to use removeAllLogins when that method supports a since date
1333050: P5 Implement clearing of IndexedDB and LocalStorage in browsingData API
§ 14 functions
supported chrome.browsingData.removePluginData() rank 981
supported chrome.browsingData.removeFormData() rank 985
supported chrome.browsingData.settings() rank 375
not supported no equivalent chrome.browsingData.removeFileSystems()no docs rank 986
supported chrome.browsingData.remove() rank 194
supported chrome.browsingData.removeHistory() rank 237
supported chrome.browsingData.removeCookies() rank 244
not supported no equivalent chrome.browsingData.removeWebSQL()no docs rank 980
not supported chrome.browsingData.removeLocalStorage()no docs rank 983
not supported chrome.browsingData.removeAppcache()no docs rank 988
supported chrome.browsingData.removeDownloads() rank 239
supported chrome.browsingData.removePasswords() rank 982
supported chrome.browsingData.removeCache() rank 245
not supported chrome.browsingData.removeIndexedDB()no docs rank 984

§ commands   desktop

Firefox docsFirefox code
§ 5 bugs
1240350: P3 [tracking] Commands API support for WebExtensions
1251795: P5 [commands] Add support for Chrome's media keys
1272130: P5 Command description is not localized
1289181: P4 Display a helpful warning when a command entry will fail to register.
1295276: P3 [commands] Handle _execute_browser_action correctly when a pageAction popup is displayed.
§ 1 functions
supported chrome.commands.getAll() rank 209
§ 1 events
supported chrome.commands.onCommand rank 79

§ contentSettings  not yet

§ 0 bugs

§ contextMenus   desktop

Firefox docsFirefox code
§ 5 bugs
1215376: P5 Implement onBeforeShow event
1269062: P2 [tracking] ContextMenus API support for Android WebExtensions
1280370: P4 contextMenus do not support other protocols (ex. 'magnet:*', 'acestream:*', 'sop:*')
1321544: -- Set a different icon for a contextMenus item
1325814: -- contextMenus.OnClickData should provide selector of the clicked element
§ 5 functions
supported chrome.contextMenus.removeAll() rank 50
supported chrome.contextMenus.createInternal()no docs
supported chrome.contextMenus.create() rank 15
supported chrome.contextMenus.update() rank 95
supported chrome.contextMenus.remove() rank 90
§ 1 events
supported chrome.contextMenus.onClicked rank 52
§ 1 properties
supported chrome.contextMenus.ACTION_MENU_TOP_LEVEL_LIMIT

§ contextualIdentities   android  desktop

Firefox docsFirefox code
§ 2 bugs
1339610: -- Not possible to use the contextualIdentity API icon
1339962: -- ContextualIdentity API colour isn't a css colour
§ 5 functions
supported chrome.contextualIdentities.query()
supported chrome.contextualIdentities.create()
supported chrome.contextualIdentities.update()
supported chrome.contextualIdentities.remove()
supported chrome.contextualIdentities.get()

§ cookies   desktop  android

Firefox docsFirefox code
§ 4 bugs
1210997: P5 See if we can use nsCookieService for cookie matching in chrome.cookies
1272953: -- Error handling for WebExtension cookies API
1309637: P2 Private cookie set by cookies.set disappears within a second when the private window was just opened
1318948: P1 WebExtension cookies API does not work in private browsing
§ 5 functions
supported chrome.cookies.getAllCookieStores() rank 314
supported chrome.cookies.getAll() rank 63
supported chrome.cookies.set() rank 60
supported chrome.cookies.remove() rank 101
supported chrome.cookies.get() rank 53
§ 1 events
supported chrome.cookies.onChanged rank 154

§ debugger  not yet

§ 0 bugs

§ declarativeContent  not yet

§ 0 bugs

§ desktopCapture  not yet

§ 0 bugs

§ devtools.inspectedWindow   desktop

Firefox docsFirefox code
§ 2 bugs
1211859: P2 Implement devtools API for open extension API
1300590: P2 Implement support for $0 and inspect bindings in devtools.inspectedWindow.eval
§ 3 functions
supported chrome.devtools.inspectedWindow.reload()no docs
supported chrome.devtools.inspectedWindow.eval()no docs
not supported chrome.devtools.inspectedWindow.getResources()no docs
§ 2 events
not supported chrome.devtools.inspectedWindow.onResourceAddedno docs
not supported chrome.devtools.inspectedWindow.onResourceContentCommittedno docs
§ 1 properties
supported chrome.devtools.inspectedWindow.tabIdno docs

§ devtools.network   desktop

Firefox docs
§ 4 bugs
1211859: P2 Implement devtools API for open extension API
1311171: P3 Implements the devtools.network.onRequestFinished API event
1311177: P3 Implements the devtools.network.getHAR API method
1341089: P1 devtools.network.onNavigated should be fired when the target page has been navigated
§ 1 functions
not supported chrome.devtools.network.getHAR()no docs
§ 2 events
not supported chrome.devtools.network.onRequestFinishedno docs
supported chrome.devtools.network.onNavigatedno docs

§ devtools.panels   desktop

Firefox docs
§ 2 bugs
1211859: P2 Implement devtools API for open extension API
1340529: P2 Fix shown/hidden events for a devtools_panel toggled from toolbox preferences
§ 3 functions
not supported chrome.devtools.panels.openResource()no docs
supported chrome.devtools.panels.create()no docs
not supported chrome.devtools.panels.setOpenResourceHandler()no docs
§ 2 properties
supported chrome.devtools.panels.sourcesno docs
supported chrome.devtools.panels.elementsno docs

§ downloads   desktop  android

Firefox docsFirefox code
§ 17 bugs
1213445: P5 [tracking] Implement chrome.downloads
1245645: P3 Implement chrome.downloads.acceptDanger()
1245648: P3 Implement chrome.downloads.drag()
1245652: P3 Implement chrome.downloads.onDeterminingFilename
1247794: P2 support persistent identifiers in chrome.downloads.*
1254327: P3 browser.downloads.download() doesn't handle redirects
1255507: P3 Handle old downloads in chrome.downloads
1255629: P5 chrome.downloads.* tests with legacy downloads
1256243: P5 extra chrome.downloads.onChanged events generated during cancel
1256269: P5 Support endTime and estimatedEndTime in DownloadItem
1256691: P5 Add test coverage for chrome.downloads.show() error states
1298215: P3 Provide an API to show the downloads manager
1300340: P3 Intermittent TEST-UNEXPECTED-TIMEOUT | toolkit/components/extensions/test/xpcshell/test_ext_downloads_download.js | Test timed out
1305002: P2 chrome.downloads.pause() should detect when a download cannot be resumed
1305663: P3 Support downloadItem.byExtensionId
1323414: P2 Add streaming support to downloads
1338381: P3 Fix downloads API tests on Android
§ 14 functions
supported chrome.downloads.search() rank 121
supported chrome.downloads.pause() rank 266
supported chrome.downloads.getFileIcon() rank 272
supported chrome.downloads.resume() rank 271
supported chrome.downloads.show() rank 243
supported chrome.downloads.removeFile() rank 252
supported chrome.downloads.cancel() rank 218
not supported chrome.downloads.drag() rank 311
supported chrome.downloads.erase() rank 223
not supported chrome.downloads.acceptDanger() rank 273
supported chrome.downloads.showDefaultFolder() rank 257
supported chrome.downloads.download() rank 92
not supported no equivalent chrome.downloads.setShelfEnabled() rank 247
supported chrome.downloads.open() rank 228
§ 3 events
supported chrome.downloads.onChanged rank 123
supported chrome.downloads.onCreated rank 222
supported chrome.downloads.onErased rank 324

§ extension   desktop  android

Firefox docsFirefox code
§ 0 bugs
§ 6 functions
supported chrome.extension.getBackgroundPage() rank 11
supported chrome.extension.getURL() rank 1
not supported no equivalent chrome.extension.setUpdateUrlData() rank 269
supported chrome.extension.getViews() rank 58
supported chrome.extension.isAllowedFileSchemeAccess() rank 217
supported chrome.extension.isAllowedIncognitoAccess() rank 202
§ 2 events
not supported deprecated chrome.extension.onRequest rank 20
not supported deprecated chrome.extension.onRequestExternal rank 113
§ 2 properties
supported chrome.extension.inIncognitoContext
supported chrome.extension.lastError

§ fontSettings  unlikely

§ 0 bugs

§ gcm  unlikely

§ 0 bugs

§ history   desktop

Firefox docsFirefox code
§ 4 bugs
1275633: P3 Add typedCount to the result set returned by browser.history.search
1280582: P4 Implement browser.history.onTitleChanged
1287928: P3 Update browser.history.onVisited to use the title from the onVisit event
1314123: P3 block moz-extension from history?
§ 6 functions
supported chrome.history.search() rank 72
supported chrome.history.addUrl() rank 242
supported chrome.history.deleteRange() rank 250
supported chrome.history.deleteAll() rank 232
supported chrome.history.getVisits() rank 189
supported chrome.history.deleteUrl() rank 191
§ 2 events
supported chrome.history.onVisited rank 200
supported chrome.history.onVisitRemoved rank 249

§ i18n   desktop  android

Firefox docsFirefox code
§ 0 bugs
§ 4 functions
supported chrome.i18n.getUILanguage() rank 144
supported chrome.i18n.getMessage() rank 10
supported chrome.i18n.detectLanguage() rank 745
supported chrome.i18n.getAcceptLanguages() rank 105

§ identity   desktop

Firefox docsFirefox code
§ 0 bugs
§ 6 functions
supported chrome.identity.getRedirectURL() rank 214
not supported no equivalent chrome.identity.getAuthToken()no docs rank 116
not supported no equivalent chrome.identity.getAccounts()no docs
not supported no equivalent chrome.identity.getProfileUserInfo()no docs rank 203
supported chrome.identity.launchWebAuthFlow() rank 156
not supported no equivalent chrome.identity.removeCachedAuthToken()no docs rank 164
§ 1 events
not supported no equivalent chrome.identity.onSignInChangedno docs rank 236

§ idle   desktop  android

Firefox docsFirefox code
§ 0 bugs
§ 2 functions
supported chrome.idle.queryState() rank 181
supported chrome.idle.setDetectionInterval() rank 196
§ 1 events
supported chrome.idle.onStateChanged rank 148

§ management   desktop  android

Firefox docsFirefox code
§ 4 bugs
1280236: P5 Implement chrome.management.uninstall
1282981: P5 Implement management.get and getAll
1282982: P5 Implement chrome.management.setEnabled
1282984: P5 Implement chrome.management events
§ 4 functions
supported chrome.management.uninstallSelf() rank 130
not supported chrome.management.getAll() rank 46
supported chrome.management.getSelf() rank 136
not supported chrome.management.get() rank 141

§ notifications   desktop  android

Firefox docsFirefox code
§ 5 bugs
1190681: P3 Browser extension |notifications| API needs support for buttons in notifications
1254300: P3 Calling notifications.create always dismisses existing notifications
1276214: P3 Add an interface to mock notifications events
1280875: -- Add an event for all notifications that are being shown
1335659: -- Add silent option for WebExtension Notifications
§ 5 functions
supported chrome.notifications.clear() rank 42
supported chrome.notifications.create() rank 28
supported chrome.notifications.getAll() rank 188
not supported chrome.notifications.update() rank 176
not supported chrome.notifications.getPermissionLevel()no docs rank 221
§ 5 events
not supported chrome.notifications.onPermissionLevelChangedno docs rank 307
not supported chrome.notifications.onShowSettingsno docs rank 277
supported chrome.notifications.onClosed rank 93
supported chrome.notifications.onButtonClicked rank 65
supported chrome.notifications.onClicked rank 40

§ omnibox   desktop

Firefox docsFirefox code
§ 3 bugs
1166831: P3 [tracking] Omnibox API support for WebExtensions
1276598: -- Provide ability to apply custom filter for search results of the location bar
1339250: P3 [omnibox] "TypeError: this._searchFinishedCallback is not a function"
§ 2 functions
supported chrome.omnibox.setDefaultSuggestion() rank 106
supported chrome.omnibox.addSuggestions()no docs
§ 4 events
supported chrome.omnibox.onInputEntered rank 74
supported chrome.omnibox.onInputChanged rank 91
supported chrome.omnibox.onInputStarted rank 161
supported chrome.omnibox.onInputCancelled rank 162

§ pageAction   android  desktop

Firefox docsFirefox code
§ 4 bugs
1237377: P2 [meta] WebExtension popup support
1263005: P3 [tracking] PageAction API support for Android WebExtensions
1267354: P3 [PageAction] Add support for chrome.pageAction.setIcon on Android
1300811: P2 [PageAction] Support show/hide on a per tab basis on Android.
§ 7 functions
supported chrome.pageAction.hide() rank 99
supported chrome.pageAction.show() rank 32
supported chrome.pageAction.setTitle() rank 98
supported chrome.pageAction.setPopup() rank 132
supported chrome.pageAction.getTitle() rank 283
supported chrome.pageAction.getPopup() rank 595
supported chrome.pageAction.setIcon() rank 77
§ 1 events
supported chrome.pageAction.onClicked rank 71

§ pageCapture  not yet

§ 1 bugs
1261339: P3 Implement chrome.pageCapture

§ permissions 

Firefox docs
§ 7 bugs
1197420: P1 (tracking) Implement permissions API and optional_permissions manifest property for open extension API
1308292: -- (tracking) Webextensions required permissions handling
1308302: P2 Display permissions prompt before downloading when installing a webextension from AMO
1308308: P5 Implement new download indicators for AMO webextension installation
1329942: P3 Misaligned icon and webextension name in permissions doorhanger
1338370: P2 Required permission support for Android
1338371: P2 Optional permission support for Android

§ power  unlikely

§ 0 bugs

§ printerProvider  unlikely

§ 0 bugs

§ privacy   android  desktop

Firefox docsFirefox code
§ 2 bugs
1340156: -- Implement browser.privacy onChange event
1341277: P3 Update privacy API to allow for disabling/enabling settings over disable/enable and updates of extensions

§ privacy.network 

Firefox docs
§ 0 bugs
§ 2 properties
supported chrome.privacy.network.networkPredictionEnabledno docs
supported chrome.privacy.network.webRTCIPHandlingPolicyno docs

§ privacy.websites 

Firefox docs
§ 0 bugs
§ 4 properties
supported chrome.privacy.websites.hyperlinkAuditingEnabledno docs
not supported chrome.privacy.websites.thirdPartyCookiesAllowedno docs
not supported chrome.privacy.websites.referrersEnabledno docs
not supported chrome.privacy.websites.protectedContentEnabledno docs

§ proxy 

Firefox docs
§ 8 bugs
1283639: P1 [tracking] Proxy API support for WebExtensions
1295807: -- Support proxy configuration from WebExtensions
1319630: -- Add support for the new "SYSTEM" return type to FindProxyForURL
1319631: -- Add support for the new "WPAD" return type to FindProxyForURL
1319634: -- Add support for the new "PASS" return type to FindProxyForURL
1319641: -- Consider supporting user authentication in FindProxyForURL
1319642: -- Add a log to track which proxies have loaded each URL.
1337001: -- Provide path and query components to non-https URLs

§ runtime   desktop  android

Firefox docsFirefox code
§ 9 bugs
1213473: P2 Complete the implementation of chrome.runtime
1223425: P3 port.onDisconnect isn't fired when extension is disabled/uninstalled
1259944: P3 runtime.sendMessage does not handle the three-argument form correctly.
1267362: P3 Provide code signature validation of native messaging host executable
1268594: P5 Support TypedArray in native messaging
1313644: P5 Temporary directory not cleaned up properly if AddonTestUtils is imported after ExtensionTestUtils is initialized.
1313648: P2 Add support for the previousVersion property to runtime.onInstalled
1313653: P5 We shouldn't need both extension.unload() and updated_addon.uninstall() in the addon update test.
1323938: P3 browser.runtime.oninstalled does not fire when extension is installed temporarily
§ 15 functions
supported chrome.runtime.getBackgroundPage() rank 80
supported chrome.runtime.openOptionsPage() rank 124
supported chrome.runtime.sendNativeMessage() rank 122
supported chrome.runtime.getBrowserInfo()
supported chrome.runtime.connectNative() rank 179
supported chrome.runtime.setUninstallURL() rank 69
supported chrome.runtime.getURL() rank 62
supported chrome.runtime.getManifest() rank 23
not supported chrome.runtime.requestUpdateCheck() rank 143
supported chrome.runtime.reload() rank 86
supported chrome.runtime.sendMessage() rank 4
supported chrome.runtime.connect() rank 47
supported chrome.runtime.getPlatformInfo() rank 149
not supported no equivalent chrome.runtime.getPackageDirectoryEntry() rank 281
not supported no equivalent chrome.runtime.restart()no docs
§ 11 events
not supported chrome.runtime.onSuspendCanceled rank 255
not supported chrome.runtime.onRestartRequired rank 336
not supported chrome.runtime.onBrowserUpdateAvailable
supported chrome.runtime.onConnect rank 41
not supported chrome.runtime.onMessageExternal rank 78
supported chrome.runtime.onUpdateAvailable rank 127
supported chrome.runtime.onStartup rank 82
supported chrome.runtime.onInstalled rank 16
not supported chrome.runtime.onConnectExternal rank 184
supported chrome.runtime.onMessage rank 3
not supported chrome.runtime.onSuspend rank 131
§ 2 properties
supported chrome.runtime.lastError
supported chrome.runtime.id

§ sessions   desktop

Firefox docsFirefox code
§ 3 bugs
1308059: P5 Implement sessions.getDevices WebExtensions API
1321365: -- Tab session history (back/forwards)
1322060: P3 Add WE API to provide functions of `SessionStore.setWindowValue` and `SessionStore.setTabValue`
§ 3 functions
supported chrome.sessions.getRecentlyClosed() rank 227
supported chrome.sessions.restore() rank 226
not supported no equivalent chrome.sessions.getDevices()no docs rank 294
§ 1 events
supported chrome.sessions.onChanged rank 293
§ 1 properties
supported chrome.sessions.MAX_SESSION_RESULTS

§ storage   desktop  android

Firefox docsFirefox code
§ 9 bugs
1213475: P2 Complete the implementation of chrome.storage
1277612: P3 [kinto] Migrate browser.storage.local to use kinto collections
1311510: P3 chrome.storage.sync: performance test of production stack for chrome.storage.sync
1311513: P3 chrome.storage.sync: develop sharding strategy
1311516: P3 chrome.storage.sync: implement client-side quotas
1311710: -- chrome.storage.sync: phase 2
1311762: P3 chrome.storage.sync: clean up and simplify based on new features of Kinto.js
1311764: P5 chrome.storage.sync: support syncing to self-hosted
1316442: P3 chrome.storage.sync: Implement syncing on Android
§ 1 events
supported chrome.storage.onChanged rank 45
§ 3 properties
supported chrome.storage.local
not supported chrome.storage.managed
supported chrome.storage.sync

§ system.cpu  unlikely

§ 0 bugs

§ system.memory  unlikely

§ 0 bugs

§ system.storage  unlikely

§ 0 bugs

§ tabCapture  not yet

§ 0 bugs

§ tabs   android  desktop

Firefox docsFirefox code
§ 9 bugs
1209869: P2 tabs.sendMessage does not send messages to tab pages
1238314: P2 Implement browser.tabs opener functionality
1246693: P3 Provide WebExtension Thumbnail API
1269456: P2 Add permission to allow extensions to load semi-privileged URLs
1315616: P3 Give extensions access to cached favicon URLs
1322485: P3 Implement tabs.discard method
1323311: P3 browser.tabs.move() - unexpected behavior of resulting tab placement position when moving several tabs preceding move-to index
1329507: -- tabs.onUpdated should have a filter template like webRequest.onBeforeRequest
1333837: -- [meta] Tab management enhancements (existing tab infrastructure)
§ 24 functions
supported chrome.tabs.executeScript() rank 6
supported chrome.tabs.getZoomSettings() rank 357
supported chrome.tabs.move() rank 126
supported chrome.tabs.getZoom() rank 254
supported chrome.tabs.connect() rank 118
supported chrome.tabs.query() rank 2
not supported deprecated chrome.tabs.sendRequest() rank 48
supported chrome.tabs.create()
supported chrome.tabs.duplicate() rank 233
supported chrome.tabs.detectLanguage() rank 207
supported chrome.tabs.insertCSS() rank 59
supported chrome.tabs.get() rank 25
supported chrome.tabs.getCurrent() rank 57
supported chrome.tabs.update() rank 8
supported chrome.tabs.setZoom() rank 261
supported chrome.tabs.setZoomSettings() rank 381
not supported no equivalent chrome.tabs.getSelected() rank 17
supported chrome.tabs.remove() rank 24
supported chrome.tabs.captureVisibleTab() rank 51
supported chrome.tabs.reload() rank 49
supported chrome.tabs.sendMessage() rank 9
supported chrome.tabs.highlight() rank 193
supported chrome.tabs.removeCSS()
not supported deprecated chrome.tabs.getAllInWindow() rank 44
§ 13 events
supported chrome.tabs.onHighlighted rank 175
not supported chrome.tabs.onActiveChanged rank 111
supported chrome.tabs.onUpdated rank 5
supported chrome.tabs.onAttached rank 139
supported chrome.tabs.onMoved rank 183
supported chrome.tabs.onDetached rank 170
not supported no equivalent chrome.tabs.onHighlightChanged rank 493
supported chrome.tabs.onZoomChange rank 333
supported chrome.tabs.onCreated rank 35
not supported no equivalent chrome.tabs.onSelectionChanged rank 96
supported chrome.tabs.onRemoved rank 26
supported chrome.tabs.onActivated rank 36
supported chrome.tabs.onReplaced rank 83
§ 1 properties
supported chrome.tabs.TAB_ID_NONE

§ theme   desktop

Firefox docsFirefox code
§ 0 bugs
§ 1 functions
supported chrome.theme.update()no docs

§ topSites   desktop  android

Firefox docsFirefox code
§ 0 bugs
§ 1 functions
supported chrome.topSites.get() rank 76

§ tts  no

§ 0 bugs

§ ttsEngine  unlikely

§ 0 bugs

§ webNavigation   desktop  android

Firefox docsFirefox code
§ 9 bugs
1190329: P3 Test coverage for webNavigation extension API
1190687: P1 Implement webNavigation.onCreatedNavigationTarget
1213478: P2 Complete the implementation of chrome.webNavigation
1248418: P3 Implement errorOccurred in the webNavigation.getFrame/getAllFrames frame details
1248426: P5 Log a warning message if the deprecated processId property is used in the webNavigation API methods
1252129: P5 Filter out webNavigation events related to new window initialization phase
1262957: P5 use NavHistoryService visit's transitionType to enhance the webNavigation transition types and qualifiers
1264936: P3 Support server_redirect transitionQualifiers on sub-frame WebNavigation events
1331128: P2 [tracking] WebNavigation API support for Android WebExtensions
§ 2 functions
supported chrome.webNavigation.getFrame() rank 306
supported chrome.webNavigation.getAllFrames() rank 231
§ 9 events
supported chrome.webNavigation.onReferenceFragmentUpdated rank 206
supported chrome.webNavigation.onCompleted rank 100
supported chrome.webNavigation.onHistoryStateUpdated rank 135
not supported chrome.webNavigation.onCreatedNavigationTarget rank 114
supported chrome.webNavigation.onTabReplaced rank 152
supported chrome.webNavigation.onBeforeNavigate rank 87
supported chrome.webNavigation.onCommitted rank 97
supported chrome.webNavigation.onDOMContentLoaded rank 107
supported chrome.webNavigation.onErrorOccurred rank 125

§ webRequest   desktop  android

Firefox docsFirefox code
§ 8 bugs
1210990: P2 Implement content-side hooks to handle WebRequest decisions which affect or are affected by the DOM.
1213483: P1 Complete the implementation of chrome.webRequest
1255894: P2 Support a webRequest.onResponseData event to filter HTTP response bytes as they come
1256122: P2 webRequest.onHeadersReceived no redirect to extension page
1268885: P2 Support full native paths in the requestBody.raw[x].file property
1273281: P3 Prevent extensions from changing security headers without a separate permission
1290016: P2 tabs.executeScript in webRequest.onCompleted gives "Unchecked lastError value: Error: No matching message handler"
1330600: -- the webrequest needs to contain additional information about the cause of the download
§ 1 functions
supported chrome.webRequest.handlerBehaviorChanged() rank 199
§ 9 events
supported chrome.webRequest.onCompleted rank 88
supported chrome.webRequest.onHeadersReceived rank 68
supported chrome.webRequest.onBeforeRedirect rank 102
supported chrome.webRequest.onAuthRequired rank 129
supported chrome.webRequest.onBeforeSendHeaders rank 81
supported chrome.webRequest.onErrorOccurred rank 89
supported chrome.webRequest.onResponseStarted rank 134
supported chrome.webRequest.onSendHeaders rank 142
supported chrome.webRequest.onBeforeRequest rank 38
§ 1 properties
supported chrome.webRequest.MAX_HANDLER_BEHAVIOR_CHANGED_CALLS_PER_10_MINUTES

§ webstore 

Firefox docs
§ 0 bugs

§ windows   desktop

Firefox docsFirefox code
§ 5 bugs
1213484: P2 Complete the implementation of chrome.windows
1253129: P3 Support focused=false in the browser.windows.create
1261963: P3 createData should be optional for browser.windows.create
1275275: P4 New windows should not be animated to their final size/position
1284273: P4 WebExtensions: chrome.windows.create creates windows with incorrect size if window does not have title bar
§ 7 functions
supported chrome.windows.get() rank 73
supported chrome.windows.getCurrent() rank 43
supported chrome.windows.create() rank 27
supported chrome.windows.getAll() rank 33
supported chrome.windows.update() rank 39
supported chrome.windows.remove() rank 70
supported chrome.windows.getLastFocused() rank 109
§ 3 events
supported chrome.windows.onRemoved rank 67
supported chrome.windows.onCreated rank 117
supported chrome.windows.onFocusChanged rank 55
§ 2 properties
supported chrome.windows.WINDOW_ID_NONE
supported chrome.windows.WINDOW_ID_CURRENT

§Permissions

Permissions supported in the manifest. For a definitive list, see MDN.

§ Manifest

Manifest keys supported in the manifest. For a definitive list, see MDN.

§ Firefox store compatibility

Also known as addons.mozilla.org.

WebExtension 1828
Total 19976
Name Trackers Blocking bugs WebExtension
# Adblock Plus
{d10d0bf8-f5b5-c8b4-a8b2-2b9879e08c5d} • 20619547 users
1226547
9 1190687
1210990
1211859
1213483
1269062
1271354
1302504
1305237
1310037
# Video DownloadHelper
{b9db16a4-6edc-47ec-a1f4-b86292ed211d} • 4452660 users
1310316
4 1246236
1255894
1271553
1323414
# Easy Screenshot
easyscreenshot@mozillaonline.com • 2403045 users
# NoScript Security Suite
{73a6fe31-595d-460b-a920-fcc0f8843232} • 2146154 users
1214733
6 1210990
1213478
1213483
1255894
1305237
1332273
# DownThemAll!
{DDC359D1-844A-42a7-9AA1-88A850A938A8} • 1294978 users
# Ghostery
firefox@ghostery.com • 1464992 users
WebExtension
# Greasemonkey
{e4a8a97b-f2ed-450b-b12d-ee082ba24781} • 1302204 users
1334174
0
# Flash Video Downloader - YouTube HD Download [4K]
artur.dubovoy@gmail.com • 1066245 users
# FlashGot Mass Downloader
{19503e42-ca3c-4c27-b1e2-9cdb2170ee34} • 848724 users
# Download YouTube Videos as MP4
{b9bfaf1c-a63f-47cd-8b9a-29526ced9060} • 1075158 users
# Tab Mix Plus
{dc572301-7619-498c-a57d-39143191b318} • 842022 users
# uBlock Origin
uBlock0@raymondhill.net • 1154406 users
1309926
1 1190687
# Element Hiding Helper for Adblock Plus
elemhidehelper@adblockplus.org • 655424 users
# Flashblock
{3d7eb24f-2740-49df-8937-200b1cc08f8a} • 595268 users
# Google Translator for Firefox
translator@zoli.bod • 798165 users
# Stylish
{46551EC9-40F0-4e47-8E18-8E5CF550CFB8} • 481414 users
# 1-Click YouTube Video Download
YoutubeDownloader@PeterOlayev.com • 694409 users
# Download Flash and Video
{bee6eb20-01e0-ebd1-da83-080329fb9a3a} • 682182 users
# Flagfox
{1018e4d6-728f-4b20-ad56-37578a4de76b} • 525145 users
# YouTube™ Video and Audio Downloader
feca4b87-3be4-43da-a1b1-137c24220968@jetpack • 727036 users
# YouTube mp3
info@youtube-mp3.org • 514302 users
# Web Developer
{c45c406e-ab73-11d8-be73-000a95be3b12} • 493583 users
# BetterPrivacy-signed
{d40f5e7b-d2cf-4856-b441-cc613eeffbe3} • 480695 users
# FireFTP
{a7c6cf7f-112c-4500-a7ea-39801a327e5f} • 490402 users
# Download Statusbar
{D4DD63FA-01E4-46a7-B6B1-EDAB7D6AD389} • 331909 users
# IE Tab V2 (Enhanced IE Tab)
{1BC9BA34-1EED-42ca-A505-6D2F1A935BBB} • 515934 users
# anonymoX
client@anonymox.net • 549250 users
# iMacros for Firefox
{81BF1D23-5F17-408D-AC6B-BD6DF7CAF670} • 397613 users
# EPUBReader
{5384767E-00D9-40E9-B72F-9CC39D655D6F} • 424322 users
1341098
2 1256122
1341341
# Personas Plus
personas@christopher.beard • 312913 users
# Speed Dial
{64161300-e22b-11db-8314-0800200c9a66} • 378805 users
# Classic Theme Restorer
ClassicThemeRestorer@ArisT2Noia4dev • 436611 users
# Lightbeam for Firefox
jid1-F9UJ2thwoAm5gQ@jetpack • 509680 users
# Ant Video Downloader
anttoolbar@ant.com • 407227 users
# Evernote Web Clipper
{E0B8C461-F8FB-49b4-8373-FE32E9252800} • 391479 users
WebExtension
# FireGestures
firegestures@xuldev.org • 363752 users
# iCloud Bookmarks
firefoxdav@icloud.com • 383932 users
# User Agent Switcher
{e968fc70-8f95-4ab9-9e79-304de2a71ee1} • 343383 users
# Easy Youtube Video Downloader Express
{b9acf540-acba-11e1-8ccb-001fd0e08bd4} • 326119 users
# Garmin Communicator
{195A3098-0BD5-4e90-AE22-BA1C540AFD1E} • 418313 users
# Google Translate, ImTranslator, Dictionary, TTS
{9AA46F4F-4DC7-4c06-97AF-5035170634FE} • 336652 users
# Xmarks Sync
foxmarks@kei.com • 337623 users
# LastPass Password Manager
support@lastpass.com • 745753 users
# FoxyProxy Standard
foxyproxy@eric.h.jung • 286381 users
# ProxTube - Unblock YouTube
ich@maltegoetz.de • 311056 users
# YouTube Flash Player
jid1-HAV2inXAnQPIeA@jetpack • 402546 users
# NetVideoHunter
netvideohunter@netvideohunter.com • 278207 users
# YouTube High Definition
{7b1bf0b6-a1b9-42b0-b75d-252036438bdc} • 284115 users
# Provider for Google Calendar
{a62ef8ec-5fdc-40c2-873c-223b8a6925cc} • 338360 users
# Session Manager
{1280606b-2510-4fe0-97ef-9b5a22eafe30} • 288482 users
# QuickJava
{E6C1199F-E687-42da-8C24-E7770CC3AE66} • 274114 users
# ColorZilla
{6AC85730-7D0F-4de0-B3FA-21142DD85326} • 273013 users
WebExtension
# Full Web Page Screenshots (♥♥♥♥♥)
{0b457cAA-602d-484a-8fe7-c1d894a011ba} • 279529 users
# VKontakte.ru Downloader (music/videos/photos @ VK)
vk@sergeykolosov.mp • 275379 users
# Disconnect
2.0@disconnect.me • 283780 users
WebExtension
# ColorfulTabs
{0545b830-f0aa-4d7e-8820-50a4629a56fe} • 250595 users
# YouTube Flash Video Player
{f3bd3dd2-2888-44c5-91a2-2caeb33fb898} • 299809 users
# S3.Google Translator
s3google@translator • 369330 users
# Mozilla Firefox hotfix
firefox-hotfix@mozilla.org • 283311 users
# Video Downloader professional
ffext_basicvideoext@startpage24 • 258678 users
# Search and New Tab by Yahoo
jid1-16aeif9OQIRKxA@jetpack • 582449 users
# AdBlocker Ultimate
adblockultimate@adblockultimate.net • 357692 users
# New Tab by Yahoo
jid1-G80Ec8LLEbK5fQ@jetpack • 318370 users
# AdBlocker for YouTube™
jid1-q4sG8pYhq8KGHs@jetpack • 314420 users
WebExtension
# ZenMate Security & Privacy VPN
firefox@zenmate.com • 285639 users
WebExtension
# frigate
e67f8350-7edf-11e3-baa7-0800200c9a66@fri-gate.org • 258320 users
# Easy Access
quicklaunch@mozillaonline.com • 303194 users
# Yandex.Bar
yasearch@yandex.ru • 452947 users
# Amazon Assistant for Firefox
abb@amazon.com • 280014 users
# ImportExportTools
{3ed8cc52-86fc-4613-9026-c1ef969da4c3} • 349228 users
# Yahoo Toolbar and New Tab
{635abd67-4fe9-1b23-4f01-e679fa7484c1} • 716458 users

§ New APIs

Looking for new APIs? Then check out WebExtensions Experiments.

§ Chrome store compatibility

Please see a blog post on this.

Source on github.