Browser.cache.memory.capacity File
Type your desired value in kilobytes and click the checkmark (or press Enter). Restart your browser to ensure the changes take effect. Recommended Values for Different Needs
Beyond raw speed, there are strategic reasons to leverage the memory cache.
By default, Firefox automatically calculates this capacity based on the total RAM available on your system. If you want to revert to automatic, setting this value to -1 tells Firefox to manage the memory dynamically [5.1]. Why Adjust the Memory Cache? Browser.cache.memory.capacity
Stores (already converted to bitmap format for display) and chrome (browser interface elements). Since Firefox requires all images (JPEG, PNG, GIF, etc.) to be converted to bitmap before display, keeping decoded versions in RAM eliminates repetitive processing.
: Enhances performance for power users with ample RAM, as more assets remain "hot" and ready for immediate display. Type your desired value in kilobytes and click
Disables memory caching entirely. Not recommended unless troubleshooting major leaks. Fixed Size
For example, according to historical data from older versions, a system with 512 MB of RAM might have seen a memory cache of around 22,528 KB, while a system with 4 GB of RAM might have received roughly 30,720 KB for the cache. Today, with modern systems typically having 8 GB or more, the automatically chosen cache size can be significantly larger (e.g., 32,768 KB on many mid‑range laptops). Stores (already converted to bitmap format for display)
If the OS signals low memory, the browser temporarily halves browser.cache.memory.capacity until pressure drops.
When Firefox needs to retrieve a cached item, it checks memory cache first (fastest), then falls back to disk cache (slower), and finally makes a network request (slowest) if neither cache contains the data.
Controls whether Firefox saves cache files to your hard drive or SSD. Set to false if you want a pure "RAM-only" browsing experience that wipes data upon closing the browser.
You can think of the browser.cache.memory.capacity as a direct line of sight to your browser's memory usage. It's one of many advanced settings found on the about:config page, a powerful configuration hub that centralizes hundreds of internal preferences which are invisible in the standard settings panel. This is where you can truly fine-tune how Firefox operates.