Differences between API implementations

The browser extensions API is still an emerging standard . As a result, while it is supported by most major browsers including Firefox, Chrome, Edge, and Opera, there are differences between the various implementations. This means that some changes may be necessary to implement your extension for multiple browsers.

Among the various browsers supporting the extensions API, Firefox is the most compliant with the emerging standard, and is, therefore, your best place to start when developing browser extensions.

The differences between browsers’ extensions API implementations fall into four areas: namespace, asynchronous event handling, API coverage, and manifest keys.

Namespace

You reference all extensions API functions using a namespace, for example, browser.alarms.create({delayInMinutes}); would create an alarm in Firefox that goes off after the time specified in delayInMinutes .

There are two API namespaces in use:

  • chrome used in Chrome and Opera.
  • 浏览器 used in Firefox and Edge.

Asynchronous event handling

JavaScript provides several ways in which to handle asynchronous events. The proposed extensions API standard is to use promises. The promises approach provides significant advantages when dealing with chained asynchronous event calls.

If you are unfamiliar with how JavaScript can handle asynchronous events or promises, take a look at Getting to know asynchronous JavaScript: Callbacks, Promises and Async/Await or the MDN Using promises 页面。

Firefox is the only major browser that has implemented promises for the extensions API. All other browsers use callbacks.

API coverage

The differences in the extensions API function implementations among the browsers fall into three broad categories:

  • Lack of support for an entire function. For example, at the time of writing, Edge doesn’t provide support for the privacy 函数。
  • Variations in the support for features within a function. For example, at the time of writing, Firefox doesn’t support the notification function method onButtonClicked , while Firefox is the only browser that supports onShown .
  • Proprietary functions, supporting browser-specific features. For example, at the time of writing, containers is a Firefox-specific feature supported by the contextualIdentities 函数。

Manifest keys

The differences in the supported manifest.json keys among the browsers fall broadly into two categories:

  • Extension information attributes. For example, at the time of writing, Firefox and Opera include the developer key enabling the addition of details about the developer of the extension, as well as the author, to be recorded.
  • Extension features. For example, at the time of writing, Edge did not support the 命令 key (which enables shortcut keys to be defined for an extension).

More information

You can find more detailed information about the differences in the supported browser extensions API features in:

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  1. 浏览器扩展名
  2. 快速入门
    1. What are extensions?
    2. Your first extension
    3. Your second extension
    4. Anatomy of an extension
    5. Example extensions
    6. What next?
  3. 概念
    1. Using the JavaScript APIs
    2. Content scripts
    3. Match patterns
    4. Working with files
    5. 国际化
    6. Content Security Policy
    7. Native messaging
    8. Differences between API implementations
    9. Chrome incompatibilities
  4. 用户界面
    1. 用户界面
    2. Toolbar button
    3. Address bar button
    4. Sidebars
    5. Context menu items
    6. Options page
    7. Extension pages
    8. Notifications
    9. Address bar suggestions
    10. Developer tools panels
  5. 如何
    1. Intercept HTTP requests
    2. Modify a web page
    3. Insert external content
    4. Share objects with page scripts
    5. Add a button to the toolbar
    6. Implement a settings page
    7. Work with the Tabs API
    8. Work with the Bookmarks API
    9. Work with the Cookies API
    10. Work with contextual identities
    11. Interact with the clipboard
    12. Build a cross-browser extension
  6. Firefox differentiators
  7. JavaScript API
    1. Browser support for JavaScript APIs
    2. alarms
    3. bookmarks
    4. browserAction
    5. browserSettings
    6. browsingData
    7. captivePortal
    8. clipboard
    9. 命令
    10. contentScripts
    11. contextualIdentities
    12. Cookie
    13. devtools
    14. dns
    15. downloads
    16. events
    17. extension
    18. extensionTypes
    19. find
    20. history
    21. i18n
    22. identity
    23. idle
    24. management
    25. menus
    26. notifications
    27. omnibox
    28. pageAction
    29. permissions
    30. pkcs11
    31. privacy
    32. proxy
    33. runtime
    34. search
    35. sessions
    36. sidebarAction
    37. storage
    38. tabs
    39. theme
    40. topSites
    41. 类型
    42. userScripts
    43. webNavigation
    44. webRequest
    45. windows
  8. Manifest keys
    1. 介绍
    1. 作者
    2. background
    3. browser_action
    4. browser_specific_settings
    5. chrome_settings_overrides
    6. chrome_url_overrides
    7. 命令
    8. content_scripts
    9. content_security_policy
    10. default_locale
    11. description
    12. developer
    13. devtools_page
    14. dictionaries
    15. externally_connectable
    16. homepage_url
    17. icons
    18. incognito
    19. manifest_version
    20. name
    21. offline_enabled
    22. omnibox
    23. optional_permissions
    24. options_page
    25. options_ui
    26. page_action
    27. permissions
    28. protocol_handlers
    29. short_name
    30. sidebar_action
    31. storage
    32. theme
    33. theme_experiment
    34. user_scripts
    35. version
    36. version_name
    37. web_accessible_resources
  9. Extension Workshop
    1. Develop
    2. Publish
    3. Manage
    4. Enterprise
  10. Contact us
  11. Channels
    1. Add-ons blog
    2. Add-ons forum
    3. Add-ons chat