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Glossary

Wired memory

Memory the system needs to run, which can't be compressed, swapped or given to apps.

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What it is

Wired memory on a Mac is memory macOS keeps locked in RAM for the kernel, drivers and other data that must always be immediately available. Apple defines it as memory required by the system to operate. It can't be compressed, moved to swap or handed to apps, so apps share what's left.

In Activity Monitor it's Wired Memory under the Memory Pressure graph, next to App Memory and Compressed. A steady figure is normal. Whether the Mac has enough memory for your apps is what memory pressure tells you.

Why it matters

Wired memory is usually stable. If it is unusually large, apps have less room and memory pressure rises sooner.

In Activity Monitor

“Wired Memory” under the Memory Pressure graph in the Memory tab.

In iKnowMyMac

The memory-by-type breakdown in the Overview and the Memory tab.

In Terminal
vm_stat

“Pages wired down” is wired memory in pages; the first line gives the page size. top -l 1 | grep PhysMem shows it in gigabytes.

App memory vs wired vs compressed memory

Activity Monitor's Memory tab splits Memory Used into three parts. App Memory (application memory) is the memory your apps and their background processes asked for, and it's the part you control: quit an app or close tabs and it falls. Wired Memory belongs to macOS and stays in RAM. Compressed is app memory macOS has squeezed to make room instead of writing it to swap. Cached files are shown on their own line.

The difference that matters is what macOS can do with each kind when apps need room.

  • App memory

    What it holds
    Memory apps and their processes asked for.
    Can macOS reclaim it?
    Yes. It can compress it, or write it to swap.

  • Wired memory

    What it holds
    Memory the system needs that must stay in RAM: the kernel, drivers and other data that must be immediately available.
    Can macOS reclaim it?
    No. It stays in RAM until whatever holds it lets it go.

  • Compressed

    What it holds
    App memory macOS has compressed to make room.
    Can macOS reclaim it?
    Partly. It can be written to swap.

  • Cached files

    What it holds
    File data kept in memory nobody else is using.
    Can macOS reclaim it?
    Yes, straight away. It is dropped when apps need the room.
What macOS can do with each kind of memory when it needs room

So wired memory is the one part of “Memory Used” that macOS can't squeeze. That is why it matters when it grows, and why it rarely matters when it doesn't.

How to judge your wired memory figure

There is no single normal figure. Wired memory depends on the Mac, its chip, how much memory it has, the displays attached, the drivers and system extensions installed, and what you are doing. Judge it in context instead:

  1. Start with memory pressure. If the memory pressure graph is green, the Mac has room for your apps and the wired figure isn't slowing anything down, whatever its size.
  2. Compare it with your own baseline. Note the wired figure a few minutes after a restart with your usual apps open. A figure that stays close to that is the system doing its normal work.
  3. Tie any growth to a workload. If wired memory grows by several gigabytes during one task and falls when the task ends, the task is the reason. If it keeps growing after the task has ended, that is worth investigating.
  4. Check swap. If wired memory is large, pressure is yellow or red, and Swap Used keeps growing, the wired share is leaving too little for your apps.
Wired memory, memory pressure and swap in Terminal
top -l 1 | grep PhysMem
memory_pressure | tail -1
sysctl vm.swapusage

The PhysMem line shows used memory with the wired part in brackets, and unused memory. Run it now and again during the task you suspect, and compare.

Apple silicon and Intel Macs

On an Apple silicon Mac, the CPU and GPU share one pool of unified memory. Memory the GPU is using for graphics, video or machine learning comes out of the same RAM as everything else, so heavy GPU work, such as a local language model, can raise the memory figures you see. On an Intel Mac with a separate graphics card, the card has its own video memory, which isn't counted in the Mac's RAM.

On either kind of Mac, things that can raise the wired figure include GPU-heavy work, several or very high-resolution displays, virtual machines, and drivers or system extensions from security, VPN, audio or storage software.

Can you free wired memory?

Not directly, and you shouldn't need to. Wired memory is released when whatever holds it lets it go, so the fix is to end the workload, not to clear memory:

  • Unload a local language model you've finished with, for example with ollama stop and the model's name.
  • Shut down virtual machines and container runtimes you aren't using.
  • Disconnect a display you aren't using and see whether the figure falls.
  • If it keeps climbing with nothing running, update or remove the software that installed a driver or system extension, and restart.

If the Mac is slow

Wired memory is rarely the whole story. The memory pressure guide walks through finding which apps grew and what to close.

FAQ

Questions

Something else? support@iknowmymac.com

What is wired memory on a Mac?

Memory macOS keeps in RAM for itself: the kernel, drivers and other data that must always be immediately available. It can't be compressed, swapped or given to apps. Activity Monitor shows it as Wired Memory in the Memory tab.

Is high wired memory bad?

Not on its own. If the memory pressure graph is green, your apps have room. It's worth a look only when wired memory keeps growing after a task has ended, or when pressure is yellow or red and Swap Used keeps rising.

What is application memory on a Mac?

Application memory, shown as App Memory in Activity Monitor, is the memory your apps and their background processes are using. Unlike wired memory, macOS can compress it or move it to swap, and it falls when you quit an app. See app memory.

What's the difference between wired, app and compressed memory?

App memory is what your apps use. Wired memory is what macOS keeps in RAM for itself. Compressed is app memory macOS has squeezed to make room. Together they make up Memory Used in Activity Monitor.

How do I free wired memory on a Mac?

You can't free it directly. It's released when whatever holds it lets go, so end the workload: unload a local AI model, shut down a virtual machine, or disconnect a display you aren't using. Memory cleaner apps don't touch it.

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