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When a page is loaded, it can be cached so it doesn't need to be rerendered to be redisplayed. For e-mail and news, messages and attachments are cached as well. This preference controls whether to use memory to cache decoded images, messages, chrome (application user interface elements), and secure (https) pages. browser.cache.memory.capacity controls the maximum amount of memory to use.

Possible values and their effects


Allow decoded images, chrome, and secure pages to be cached in memory. (Default)


Don't cache decoded images, chrome, and secure pages in memory.


  • Setting this preference to false causes less memory to be used but also increases the load time of previously visited pages and dialogs, especially those of secure sites.
  • If browser.cache.disk_cache_ssl is set to true, secure pages will be stored in disk cache, not memory cache.

Recommended settings

Users who are having problems with memory consumption can try setting the value to false to lower memory consumption. Users who have no problems with memory should leave it at true.

First checked in

2001-06-27 by Darin Fisher

Has an effect in

  • Netscape (all versions since 6.1)
  • Mozilla Suite (all versions since 0.9.1)
  • Phoenix (all versions)
  • Firebird (all versions)
  • Firefox (all versions)
  • Thunderbird (all versions)
  • Minimo (all versions)
  • SeaMonkey (all versions)

Related bugs

Related preferences