tree: b5a322ee18c62b59a16d65ca2d99582bbb89ea38 [path history] [tgz]
  6. ax_event_server.h
  8. ax_tree_server.h
  10. ax_utils.h
  11. chrome-events.ps1
  12. chrome-tree.ps1
  13. chromium-events.ps1
  14. chromium-tree.ps1
  15. example-tree-filters.txt
  16. ff-events.ps1
  17. ff-tree.ps1

Inspect tools

These cli tools are designed to help to debug accessibility problems in applications, primarily in web browsers.

ax_dump_tree to inspect accessibility tree of application ax_dump_events to watch accessibility events fired by application

Note: if you are on Windows, see convenience scripts section, it makes the tools easier to use on Windows.


autoninja -C out/Default ax_dump_tree ax_dump_events

The command generates ax_dump_tree and ax_dump_events executables in out/Default directory.



  1. Turn on Accessibility for Terminal in Security & Privacy System Preferences.

  2. Some applications keep accessibility inactive, which prevents them to generate accessible trees or emit events. Thus either:

  • start VoiceOver (CMD+F5) or
  • use application specific runtime flags ** Chromium: --force-renderer-accessibility


Helps to inspect accessibility trees of applications. Trees are dumped into console.


To dump an accessible tree, run: ax_dump_tree <options>

At your convenience the number of pre-defined application selectors are available: --chrome for Chrome browser --chromium for Chromium browser --firefox for Firefox browser --safari for Safari browser

--active-tab to dump a tree of active tab of selected browser.

You can also specify an application by its title: ax_dump_tree --pattern=title

Alternatively you can dump a tree by HWND on Windows: --pid=HWND Note, to use a hex window handle prefix it with 0x.

Or by application PID on Mac and Linux: --pid=process_id

Other options: --filters=absolute_path_to_filters.txt to filter properties, use where the filters text file has a series of @ALLOW and/or @DENY lines. See example-tree-filters.txt in tools/accessibility/inspect. --help for help


The tool logs into console accessibility events fired by application.

To watch accessibility events, run: ax_dump_events <options>

Use these pre-defined application selectors to indicate application: --chrome for Chrome browser --chromium for Chromium browser --firefox for Firefox browser --safari for Safari browser

--active-tab to scope events to an active tab of selected browser.

You can also specify application by its title: --pattern=title

Or by application PID: --pid=process_id

Convenience PowerShell scripts

Note: Windows only.

Run these scripts to avoid the difficulty of looking up the process id or window handle you want to inspect. Sometimes there may be several windows open for the given app, and disambuation. In this case, after you run the script, it will list top level windows/processes and ask you to re-run with an argument that includes a substring from the window title you want to inspect the tree/events for. For example, chrome-tree live will inspect a tab with the name “Live region tests” (the title matcher is case insensitive).

  • chrome-tree and chrome-events for official Google Chrome (has ‘Google Chrome’ in the window title)
  • chromium-tree and chromium-events for Chrome you built yourself (has ‘Chromium’ in the window title)
  • ff-tree and ff-events for Firefox