What does "Your System Has Run Out of Application Memory" mean on Mac?

The short answer

Your Mac is running out of RAM because your open apps are using more memory than your computer has available.

What is application memory?

Application memory is the RAM (random access memory) your Mac uses to keep apps running. Unlike storage (your hard drive), RAM is temporary, fast memory that apps need while they’re actively open. When it fills up, your Mac can’t keep everything running smoothly and shows this warning.

Why does this happen?

This message usually appears when:

  • Too many apps are open at once — especially heavy ones like Chrome, Photoshop, or video editors
  • Browser tabs are piling up — each tab uses its own chunk of memory, and dozens of tabs can eat through RAM quickly
  • An app has a memory leak — a buggy app keeps grabbing more memory without releasing it
  • Your Mac has limited RAM — older or base-model Macs with 8 GB of RAM hit this limit more easily

How to fix it

When you see this warning, here’s what to do right away:

  1. Close apps you’re not using — click the warning’s “Force Quit” button or press Command + Option + Esc to force quit unresponsive apps
  2. Close extra browser tabs — this alone can free up a significant amount of memory
  3. Restart your Mac — this clears all memory and gives you a fresh start

Prevent it from happening again

  • Check Activity Monitor — open it from Applications > Utilities and click the Memory tab to see which apps use the most RAM
  • Quit apps when you’re done — closing a window on Mac doesn’t always quit the app; use Command + Q to fully quit
  • Keep your Mac updated — updates often include fixes for memory leaks and performance issues
  • Consider fewer browser extensions — each one runs in the background and uses memory

When should you worry?

If this message appears once in a while when you have a lot open, it’s normal. But if it keeps showing up during light use:

  • A specific app may be broken — check Activity Monitor for any app using an unusually large amount of memory, and try reinstalling it
  • Your Mac may need more RAM — if you consistently need more than your Mac has, it may be time for an upgrade (note: most modern Macs can’t have RAM added after purchase)