Why It’s Good That Your Computer’s RAM Is Full

Is Windows, Linux, Android, or another operating system using a lot of RAM? Don’t panic! Modern operating systems use RAM as a file cache to speed things up. Assuming your computer is performing well, there’s nothing to worry about.
While it may seem counterintuitive to those of us who remember our computers always being starved for RAM, high RAM usage means your RAM is being put to good use. Empty RAM is wasted RAM.

Bad High Memory Usage vs. Good High Memory Usage

First of all, high memory usage isn’t always a good thing. If your computer seems very slow, then high random access memory (RAM) usage is not a good thing. If your RAM is full, your computer is slow, and its hard drive light is constantly blinking, your computer is swapping to disk. This is a sign that your computer is using your hard disk, which is much slower to access, as an “overflow” for your memory.
If this is occurring, it’s a clear side that your computer needs more RAM – or that you need to use less memory-hungry programs. This is definitely a bad thing.
However, there’s a clear difference between this case, where your computer isn’t performing well, and the more common case where your computer seems to be performing just fine, but there’s an alarming amount of RAM being used with few programs open.

Disk Caching

Install Windows XP on a computer and you’ll probably see it using several hundred megabytes of memory when the system is idle. Install Windows 7 on that same computer and you’ll likely see Windows 7 using several gigabytes of memory in the same situation.
So what’s going on? Is Windows XP just a lighter, faster operating system? Are modern operating systems bloated and wasteful with memory? Not quite.
RAM is more plentiful than it was when Windows XP was the shiny new operating system, and modern operating systems take advantage of it. Modern operating systems use your computer’s RAM as a cache for frequently accessed files and program data.
In Windows, this feature is known as SuperFetch, which was introduced in Windows Vista. SuperFetch watches the applications you use and loads commonly-used application files and libraries into your computer’s RAM before you need them. When you launch an application, Windows loads the application’s files from your RAM instead of reading them from disk, which is a slow process. This speeds up application launching and generally makes your computer faster and more responsive.
This doesn’t just apply to Windows. Linux users will also notice that their computer is using a seemingly alarming amount of memory for caching files from your disk, and new Linux users may be concerned when they notice this. Many resource-usage-monitoring programs, such as  GNOME System Monitor, hide the memory used by the cache from the user so that users won’t have to understand this or be concerned.

Browsers and Other Software

The same applies for browsers and other software applications with their own caches. For example, if you notice a web browser like Mozilla Firefox using a large amount of RAM, that’s not necessarily a bad thing. If you have a lot of RAM in your computer, it’s good that Firefox is using it. By caching web pages you’ve visited in your RAM, Firefox can speed up web page load times, making using the Back and Forward buttons much faster. For this reason, Firefox automatically determines the ideal cache size based on the amount of RAM in your computer.
Firefox itself may have historically had memory leaks and other problems, but the concept is the same. It doesn’t make sense for Mozilla to get Firefox’s RAM usage down to the 50 megabytes because modern computers have a lot of RAM Firefox can use to speed up web browsing.
The same applies for other software. Programs with high memory usage may be making good use of your RAM, not wasting it.

Why Empty RAM is Useless

You may be thinking that using RAM as a cache is great, but you don’t want these program files and other data taking up your RAM. You’d rather have empty RAM available so that programs will launch instantly and the memory will be used for what you think is best, not what your operating system and programs think is best.
However, this isn’t a concern at all. Whether your RAM is full of cached files or completely empty, it’s all available for programs that really need it. Cached data in your RAM is marked as low-priority, and it’s instantly discarded as soon as the memory is needed for something else.
Because this data can be instantly discarded when necessary, there’s no disadvantage to using the RAM for cache. (The one potential disadvantage is users who don’t understand what’s going on becoming confused.)
Empty RAM is useless. It’s not any faster for the computer to write data to empty RAM, nor does empty RAM use less power. In fact, assuming you’re launching a program that may already be present in your RAM’s file cache, programs will load much faster when your RAM is used rather than when it’s empty.