A beautiful mind writes: It has been long claimed by users that Firefox leaks memory, and on the other hand the developers claimed the number of leaks are minimal. It turns out both groups were right. Stuart Parmenter, one of the authors of the RAMBack extension started investigating and found out that the issue is memory fragmentation. He discovered that while loading about:blank uses 12,589,696 bytes of memory in the test he performed (image), after exercising Firefox with different websites and then clearing the caches with the help of the RAMBack extension the picture is wholly different: "Our heap is now 29,999,872 bytes! 16,118,072 of that is used (up 4,634,208 bytes from before... which caches am I forgetting to clear?). The rest, a whopping 13,881,800 bytes, is in free blocks!"