Activity Monitor: What Is Free, Wired, Active, Inactive, and Used Memory in RAM

Understanding Memory Use with Activity Monitor (from MacMost.com).

You can use Activity Monitor to see how your Mac is using memory. But what do free, active, inactive and wired mean? How about page ins and page outs? Plus, learn to use them to figure out if you need more memory.

"Free memory" is the amount of memory you have available in system memory or RAM.

"Wired memory" is the hardware memory that your computer needs to use at a minimum to operate.

"Active memory" is the amount of memory that is being used in RAM right now.

"Inactive memory" is an amount of memory that might have just been used

"Used memory" is the total of all used memory -- Wired, Active, and Inactive

"Free memory" plus "Used memory" equals the size of your installed RAM memory.

If you see a lot of "Page outs", that means that your RAM is overloaded and you computer needs to use a lot of Virtual Memory -- swapping memory on the hard drive.

"Page ins" is memory being used in RAM. Page outs -- memory from outside the System Memory or RAM memory.

"Swap used" is how much virtual memory is being used.

VM size is the disk space available in your hard drive. The amount can be used to swap memory as needed to run and application or process.