XULRunner提供了一个开发xul程序的解决方案. XULRunner的目的就是提供一个部署XUL应用（目前主要是Firefox和Thunderbird）的解决方案,同时也提供一个嵌入式应用的机制。目前已经实现或计划的功能如下：
Gecko Features
- XPCOM
- Networking
- Gecko rendering engine
- DOM editing and transaction support (no UI)
- Cryptography
- XBL (XBL2)
- XUL
- SVG
- XSLT
- XML Extras (XMLHttpRequest and DOMParser)
- Web Services (SOAP)
- Auto-update support (not yet complete)
- typeahead-find toolbar
- history implementation
- accessibility support
- IPC services for communication between gecko-based apps (not yet complete)
- storage/sqlite interfaces (not yet turned on by default)
User Interface Features
The following user interface will be supplied by XULRunner, and may be overridden by embedders in certain circumstances:
- APIs and user interface for installing, uninstalling, and upgrading XUL applications. See the wikimo:XUL:Installation Story.
- Extension Manager
- File picker (will use native OS filepicker as appropriate)
- Find toolbar
- Helper app dialog/UI
- Security UI (maintenance of SSL keychains, etc)
Embedding APIs
The following embedding APIs will be provided by XULRunner:
- cross-platform embedding (XRE_InitEmbedding)
- JavaXPCOM embedding
- PyXPCOM embedding (not yet complete)
- activex control (Windows only) (not yet complete)
- gtkmozembed (Linux only) (not yet complete)
- NSView-based-widget (Mac OSX only) (not yet complete)
The "Maybe" List
The following features have been discussed and may be included if developer time permits and codesize is controlled:
- LDAP support
- Spellchecking support (with or without dictionaries provided) see bug 285977
- Core support for profile roaming (with application-specific extensibility)
What's out
XULRunner will not supply:
- Bookmarks or History UI (must be managed by the application/embedder)
- XForms (xforms will be available as an extension).