DOM Inspector

The DOM Inspector (also known as DOMi) is a developer tool used to inspect, browse, and edit the Document Object Model of documents - usually web pages or XUL windows. The DOM hierarchy can be navigated using a two-paned window that allows a variety of different views on the document and all nodes within.

This tool is an add-on for XUL-based applications such as Firefox and Thunderbird. If you are looking for the DOM inspector that's built into Firefox, see the documentation for the Page Inspector.

Documentation

Introduction to DOM Inspector
A guided tutorial that will help you get started with DOM Inspector.
DOM Inspector FAQ
Answers to common questions on DOM Inspector.
DOM Inspector page at MozillaZine
More information on the DOM Inspector.
How to build the DOM Inspector
Blog post on building the DOM Inspector from source.

Getting DOM Inspector

Firefox & Thunderbird
You may download and install the DOM Inspector from the AMO web site. (Thunderbird users browsing AMO in Firefox should save the installation link, or visit the DOM Inspector for Thunderbird page.)
Thunderbird 2
DOM Inspector for Thunderbird 2 is available from Thunderbird Add-ons. Or, build Thunderbird yourself with the following options:
ac_add_options --enable-extensions="default inspector"
ac_add_options --enable-inspector-apis
Mozilla Suite and SeaMonkey
Select Tools > Web Development > DOM Inspector. You can install the Sidebar panel via Edit > Preferences > Advanced > DOM Inspector, then simply open up the inspector panel and visit a website.

Report a bug in DOM Inspector

Use the conveniently named "DOM Inspector" component in Bugzilla.

To find out who knows DOM Inspector code and where it lives, see the DOM Inspector module listing.