iStat Menus has been the default answer to this problem for about fifteen years, and it is genuinely good software. If you are looking for an alternative, it is usually for one of two reasons: it costs money, or you noticed you use about a tenth of what it does.
I built AirStats for the second reason and then discovered the first was also true for a lot of people. So here is an honest account of the swap, including the parts where you lose something.
What AirStats is
A menu bar system monitor for macOS. Sixteen metrics you can put in the menu bar: CPU usage, CPU temperature, CPU frequency, memory usage, memory pressure, GPU usage, network up and down, disk activity, disk free, battery, battery time, system power, fan speed and uptime. Show two of them or show all sixteen.
Click the menu bar and a panel opens with per core load, memory pressure and top processes. There is a floating desktop overlay if you want the numbers off the menu bar entirely, and threshold alerts if you want a notification when something crosses a line you set.
It is free, MIT licensed, and 4.6 MB on disk. There is no account and no paid tier.
Where iStat Menus is still better
I would rather you know this before you download anything.
- It runs on Intel Macs. AirStats does not. The build is Apple silicon only and needs macOS 14 or later. If you are on an Intel Mac, stop reading, iStat Menus is your answer.
- It keeps history across launches. AirStats keeps none. Quit it and the graphs start from empty. If you care about what your machine was doing yesterday, that is a real feature and AirStats does not have it.
- Weather, and far more sensor detail. iStat Menus exposes essentially every sensor your Mac publishes, individually. AirStats samples a capped set and averages the CPU ones into a single number.
- Many more display configurations. Combined menus, dropdown layouts, per item formatting. AirStats covers the common cases and stops.
- Fifteen years of being maintained. AirStats is new. That is worth something and I am not going to pretend otherwise.
Where the swap pays
It costs nothing. No trial, no licence, no upgrade pricing when the next major version lands.
It is one process. No helper, no launch agent, nothing installed outside the app. Quit AirStats and nothing of it is left running, which is not true of most monitors in this category.
It is lighter. On the same Mac, sampled by the same command in the same window, AirStats idled at 0.046% CPU against 0.116% for the iStat Menus suite. Memory is the bigger gap on a fresh launch, though it narrows once AirStats has had its panel open for a while. The full run is here, including the parts where the gap closes.
The source is open. All of it, MIT, including the scripts that produced the numbers on this site. A system monitor is an app that reads everything about your machine, and being able to check what it does with that is worth more here than in most software.
So who should actually switch?
If you use iStat Menus for weather, historical graphs, or per sensor readouts, stay. You are using the thing it is best at and you will miss it immediately.
If you use iStat Menus because you wanted CPU and memory in your menu bar and it was the obvious app to buy, that is who AirStats is for. That is most people, in my experience, including me for about eight years.
You can run both for a day. They do not conflict, and the menu bar is the only thing they compete for.