Browser.cache.memory.capacity ((full)) 〈Windows〉

: Controls whether Firefox writes cache files to your hard drive or SSD. Setting this to false forces Firefox to only use RAM, which is ideal for protecting SSD lifespan or enhancing privacy.

| User Profile | System RAM | Recommended Value | Rationale | | :--- | :--- | :--- | :--- | | | 8 - 16 GB | -1 (Auto) | Firefox's dynamic algorithm is highly optimized for standard usage patterns. | | Developer / Power User | 32 GB | 256000 (250 MB) | Provides headroom for heavy SPAs and dev tools without starving the OS. | | Legacy Hardware | 2 - 4 GB | 25600 (25 MB) or 0 | Prevents cache from causing swapping. Disable if OS memory pressure is extreme. | | Ramdisk User | 64 GB+ | 0 (Disable) | If you mount the Firefox profile folder to a RAMdisk, disable the internal memory cache to avoid double-caching data in RAM. | | Privacy Focused | Any | 0 (Disable) | Disabling the memory cache ensures that closing the browser leaves zero trace of images or scripts in RAM (though disk cache may remain). | Browser.cache.memory.capacity

The memory cache stores web resources—such as images, scripts, CSS files, and HTML pages—directly in your computer’s RAM (Random Access Memory). Because RAM is orders of magnitude faster than a hard drive or even an NVMe SSD, retrieving a cached resource from memory allows pages to reload almost instantly, especially when using the back/forward buttons or revisiting a page in the same session. : Controls whether Firefox writes cache files to

: If you have a computer with limited RAM (e.g., 2GB or less), capping this value can prevent the browser from "hogging" memory and slowing down other applications. | | Developer / Power User | 32

Set to true by default. Changing this to false completely disables the RAM cache, rendering the capacity setting obsolete.

In the architecture of modern web browsers, specifically within the Gecko engine (Firefox), browser.cache.memory.capacity