If you don't have enough memory for a single app, then your life is completely miserable - in that case, swapping is almost indistinguishable from crashed. But

If you don't have enough memory for a single app, then your life is completely miserable - in that case, swapping is almost indistinguishable from crashed. But swap can be the difference between being able to run one app at a time, vs run three or four, as long as you only have one in the foreground at a time. Swap doesn't play well with GC, or pointerful programming languages generally. Swap is a latency hit every time you touch an evicted page, and the more pointers your structures have, the more frequently that occurs. In older times, when memory needed to be conserved, GC was less frequently used, and as a consequence of the accounting overheads of manual memory allocation, pointerful data structures weren't quite as common. Instead, you'd have pre-allocated arrays which supported up to N items of a particular type (and tough luck if you wanted more), or in more sophisticated applications, arena allocators. In such systems, the working set of memory is more likely to be contiguous; paging works better because every page load is more likely to bring in relevant data. Switching between two open applications was the moment where you'd typically hit swap; that, and every now and then when you touched an area of the app you hadn't in a while, or jumped to a distant area of the document you were working on. The HDD light would come on, and you'd have to wait a few seconds while the computer ground through (HDDs being audible, some much louder than others) before you'd switch. At some point in the mid 2000s, GC languages tipped the balance, especially JS. The browser became the main application, and wouldn't tolerate swap well. It became a mini OS unto itself, and had to balance the competing needs of different tabs. Then mobile exploded, and didn't use swap at all in order to compete with the iPhone, remarkable for its smooth animations. If there was to be latency, the application had to hide it; OS-level introduced latency on a page fault wasn't good enough, because if it happened on the UI thread, you dropped frames. And of course swap never worked well on servers with frequent requests. Swapping on a server is a great way to back up all your queues.