Memory used
Climbs to the ceiling on every Mac and stays there. Alarming to read, and almost never useful.
macOS menu bar · Apple silicon · Mac App Store
The first sign your Mac is slowing down. Now in the menu bar.
Memory pressure is the first thing to move when a Mac gets tight, and macOS keeps it buried in Activity Monitor. MemPressure keeps it in the menu bar instead, next to CPU, swap and temperatures. Low means your Mac is comfortable. High means it is time to close something.
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Live, not a screenshot. Drawn with the app's own geometry. Four of the nine readings, at the size they sit in your bar.
- Pressure
- Per-core CPU
- Compressed
- CPU
- Memory used
- Swap
- Chip temp
- SSD temp
- Battery temp
Why pressure
Built for a MacBook Air with too much open.
We run several projects at once on MacBooks, often with graphics work in the mix, and an Air has no fan noise to warn you that things are getting tight. Memory pressure is the first thing that moves. Watch it climb and you can close a browser window or quit something heavy while the machine is still fluid, instead of finding out once everything has started to stutter.
Memory used will not tell you this. macOS fills spare RAM on purpose, because caching is free performance, so a healthy Mac sits near the ceiling all day. Pressure tracks whether the system is actually struggling to keep up.
Memory pressure
Rises before the machine starts to stutter, which is the moment you can still do something about it.
Swap and compression
The mechanics behind the reading, listed on their own, so you can see why it moved.
How much it costs to run
An instrument that changes what it measures is lying to you.
MemPressure is built to stay under its own readings. Every release is measured with powermetrics, Apple's own tool, before it ships. These are the numbers for 1.5.0 on a MacBook Air.
of one CPU core
What the app itself uses with all nine readings on. Turning readings on or off does not change it.
With it, or without it
Whole-machine power was 183 mW with the app quit and 183 mW with everything running, three spinning cogs included. The cog spins for free.
Can't phone home, not won't
The app runs in the App Store sandbox with no network entitlement, so macOS itself stops it from connecting anywhere. No account, no analytics, no helper process.
Six ways to read it
Every metric, drawn the way you want it.
Pick a display style for each metric, not one for the whole app. Set the spacing, leave the colour off, and it sits in the bar like it shipped with the system.
Colour
Quiet by default. Colour when you ask.
Everything above is monochrome, because a menu bar you notice all day is a menu bar you end up hiding. Switch colour on in the settings and each widget shifts as its metric climbs, so a red cog means something instead of being decoration.
What it watches
Nine readings, one strip of menu bar.
Show the ones you care about and hide the rest. Click the bar to open the panel for the full set, the history and the settings.
Memory pressureStraight from the kernel, the same source Activity Monitor reads.
Memory usedApp memory, wired and compressed, matched to Activity Monitor.
CompressedHow much RAM the compressor is holding back right now.
SwapFlags when it approaches the size of your physical RAM.
CPUTotal load, sampled on your schedule.
Per-core CPUEvery core on its own, with P and E clusters separated.
Chip temperatureRead from the built-in sensors. No kernel extension.
SSD temperatureThe drive sensor most tools never show you.
Battery temperatureWorth a look before you shut the lid on a hot machine.
How it is built
Written for the menu bar, not ported to it.
Native, and only native
AppKit and Core Animation, with no web view and no cross-platform runtime. It draws like the system because it uses what the system uses.
Menu bar discipline
Widgets are drawn to the pixel at menu bar size, with spacing tuned to the rhythm of the system's own icons, so nothing sits crooked next to them.
Nothing in the background
No helper, no daemon, no login item unless you switch it on. Quit it and nothing of it is left running.