12 posts

Memory, explained.

What memory pressure means, why your Mac feels slow, and the words behind both.

Memory, explained

What is jetsam on Mac?

Jetsam is the kernel-level mechanism macOS uses to kill processes when memory runs critically low. Here is what it is, how it decides what to kill, and what it means for you.

Memory, explained

What does "your system has run out of application memory" mean?

The error means macOS ran out of usable RAM and had to start closing apps. It looks scary, but it isn't a sign your Mac is broken. Here's what's happening and what to do.

Memory, explained

What is unified memory on Apple Silicon?

Unified memory is one shared pool of RAM that the CPU, GPU, and Neural Engine all access without copying data between chips. Here is what that means for your Mac.

Memory, explained

What is "App Memory" in Activity Monitor on Mac?

App Memory is the slice of RAM your running apps are actively using. Here's what it means, how it differs from Wired and Cached memory, and when it actually matters.

Memory, explained

What is compressed memory on Mac?

Compressed memory is macOS squeezing inactive pages of RAM to fit more in. It has been doing this since 2013 and it is a feature, not a problem.

Memory, explained

What is kernel_task and why is it using so much CPU?

kernel_task shows 200%, 300%, or more CPU in Activity Monitor and you panic. Here is what it actually is, why that number is misleading, and how to bring it down.

Memory, explained

What is memory pressure on Mac?

Memory pressure is your Mac's honest report card on how hard it's working to keep apps responsive. Green, yellow, and red explained in plain English.

Memory, explained

What is purgeable disk space on Mac?

Purgeable space is the part of your Mac's hard drive that macOS can delete automatically when it needs room. Plain-English explanation of what it is, why it causes confusion, and when to care.

Memory, explained

What is swap on Mac?

Swap is the part of your hard drive that macOS uses as overflow when RAM gets full. Here's what it means, when it matters, and when to stop worrying.

Memory, explained

What is virtual memory on Mac?

Virtual memory lets your Mac run more apps than its physical RAM alone would allow. Here's what it actually is, how it works, and when to pay attention.

Memory, explained

What is the WindowServer process on Mac?

WindowServer draws every window, menu, and animation you see on a Mac. Here is what it does, why it sometimes uses a lot of memory, and how to calm it down.

Memory, explained

What is wired memory on Mac?

Wired memory is RAM macOS has reserved for itself - kernel data, drivers, and core OS structures that cannot be freed. Here's what it means, when it's a problem, and what you can actually do about it.