WebExtensions API Development

This documentation covers the implementation of WebExtensions inside Firefox. Documentation about existing WebExtension APIs and how to use them to develop WebExtensions is available on MDN.

To use this documentation, you should already be familiar with WebExtensions, including the anatomy of a WebExtension and permissions. You should also be familiar with concepts from Firefox development including e10s in particular.

WebExtension API Developers Guide

• Background
  • Javascript APIs
  • Manifest Keys
  • Other Considerations
• API Implementation Basics
  • The API Schema
  • The ExtensionAPI class
  • Built-in versus Experimental APIs
  • Adding a built-in API
  • Adding Experimental APIs in Privileged Extensions
  • Globals available in the API scripts global
  • WebIDL Bindings
• API Schemas
  • Implementing a fixed Javascript property
  • Schema Items
  • Describing constrained values
• Implementing a function
  • Declaring a function in the API schema
  • Implementing a function in the main process
  • Implementing a function in a child process
• Implementing an event
  • Declaring an event in the API schema
  • Implementing an event
  • Handling extra arguments to addListener()
  • Handling listener return values
  • Implementing an event in the child process
  • Event Listeners Persistence
• Implementing a manifest property
• Managing the Extension Lifecycle
  • Extension Shutdown
  • Extension Uninstall and Update
  • Handling lifecycle events
• Incognito Implementation
  • The Implementation
  • Testing
  • Testing EventManager events
  • Testing API Calls
  • Privateness of window vs. tab
• WebIDL WebExtensions API Bindings
  • Review process on changes to webidl definitions
  • Background Service Workers API Request Handling
  • Generating WebIDL definitions from WebExtensions API JSONSchema
  • Wiring up new WebExtensions WebIDL files into mozilla-central
  • Testing WebExtensions WebIDL bindings
• How webext storage works
  • WebExtension API
  • Overview of the API
  • xpcom as the interface to Rust
  • webext_storage_bridge
• Utilities for implementing APIs
  • WindowManager
  • TabManager
  • ExtensionSettingsStore
  • ExtensionPreferencesManager
  • ESS vs. EPM
  • Using ESS/EPM with experimental APIs
• WebExtensions Javascript Component Reference
  • ExtensionAPI class
  • Extension class
  • EventManager class
  • BaseContext class
  • WindowManager class
  • TabManager class