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In order to allow external applications to track what’s happening inside the browser, Mozilla implements an MSAA (Microsoft Active Accessibility) server. This lets outside programs—such as screen readers, voice recognition software, and other accessibility-enhancing applications—track focus changes, listen for events, and read window contents.

In its implementation, Mozilla keeps a hash table (cache) of every object it makes available via the MSAA server. This cache can help prevent crashes due to other applications improperly using the MSAA server, and may also speed up certain interactions with other accessibility software.

This preference exists largely for debugging purposes.

Possible values and their effects


Disable the accessibility cache and directly query Mozilla for returning MSAA server requests.


Use the internal cached information of accessible objects for returning MSAA server requests. (Default)

First checked in

2002-10-24 by Aaron Leventhal

Has an effect in

  • Netscape (all versions since 7.1)
  • Mozilla Suite (all versions since 1.2)
  • Mozilla Phoenix (all versions since 0.4)
  • Mozilla Firebird (all versions)
  • Mozilla Firefox (all versions)
  • SeaMonkey (all versions)

Related preferences

Related bugs

External links