How to control fan speed on a Mac

What macOS does on its own

Every Mac with a fan runs a closed-loop controller in firmware. It reads the temperature sensors on the chip, decides how much airflow the machine needs, and writes a target speed to each fan several times a second. You never see it and you cannot configure it.

That controller is tuned for a quiet room, not for a finished export. It lets the chip run hot for a long time before it spends any fan noise on cooling it, because for most people, most of the time, silence is the better trade. The consequence is that a sustained workload can sit near the chip’s thermal limit while the fans are still turning slowly.

This is by design, not a defect. But it is a default, and a default is only right on average. If you are the person exporting video for forty minutes, you may prefer the noise.

What a fan control app can and cannot change

The System Management Controller exposes each fan through a small set of keys. Two of them are writable: the fan’s mode, which selects firmware control or manual control, and its target speed in RPM. A fan control app flips the mode and then writes a number.

What that means in practice:

• You can raise a fan above what macOS chose. This is the whole point, and it is the case that recovers performance on a machine that is throttling.
• You can lower a fan, down to the minimum its own hardware reports. You cannot stop a fan or drive it below that floor.
• You cannot exceed the maximum the fan reports.The ceiling is the hardware’s, not the software’s.
• You cannot change the chip’s thermal limits. No fan app raises the temperature at which macOS decides to slow the processor down. It only helps you reach that temperature later, or not at all.

How to control fan speed on a Mac

Fan control needs to write to hardware, and writing to hardware needs root. That shapes the setup on any modern macOS release:

1. Confirm your Mac has a fan at all. Every Apple Silicon MacBook Air is passively cooled, so there is nothing to control on those. Check the full list of models.
2. Install a fan control app. Breeze needs an Apple Silicon Mac on macOS 15 Sequoia or later.
3. Approve its privileged helper. Breeze installs a small background service and macOS asks you to allow it once, in System Settings › General › Login Items & Extensions. There is no administrator password prompt and no kernel extension.
4. Set a speed. Breeze gives each fan its own slider, labeled with the live RPM and whether that fan is on automatic or manual.
5. Hand it back when you are done. Quitting returns every fan to firmware control, and so does “Return Fans to Automatic”.

What actually gets written to your hardware

This is worth being specific about, because “it writes to the SMC” covers both a careful tool and a reckless one. Breeze writes exactly two keys per fan: the target speed and the mode. It has no general-purpose “write any value” path, so there is no route from the app to any other part of your hardware.

Everything else it touches is read-only: the number of fans, each fan’s current speed, and each fan’s reported minimum and maximum. Temperatures come from the CPU performance and efficiency cores, the GPU, and the wider SoC package, sampled every two seconds and kept as a rolling five-minute history.

The limits that are enforced for you

A fan is a moving part in a sealed machine, so the interesting question about any fan control app is what happens when something goes wrong. Three mechanisms matter.

Speeds are clamped to what the hardware reports

Before every single write, Breeze re-reads the minimum and maximum RPM from the fan itself and clamps your requested speed into that range. It does not cache those limits, and the privileged helper repeats the check rather than trusting the app that asked. A request that is not a sensible number is refused outright instead of being rounded into range.

A watchdog hands control back if the app stops answering

While any fan is manual, Breeze checks in with its helper continuously. If those check-ins stop for thirty seconds, because the app crashed, hung, or was force-quit, the helper returns every fan it touched to automatic on its own. You do not have to be there, and the app does not have to be alive.

Automatic is restored on quit, crash, and reboot

Quitting Breeze blocks until every fan is handed back. If the helper itself is shut down it restores fans before exiting. And because the only thing it persists is a snapshot of what automatic looked like before you changed anything, a machine that lost power mid-session comes back under firmware control. Manual speeds are never restored across launches, only ever released.

What this deliberately does not do

Breeze has no fan curve editor. Manual mode is one fixed target RPM per fan, which you set and can change whenever you like, and it never adjusts your fans on its own. A curve sounds appealing, but it means software silently steering your cooling based on rules you set once and forgot, which is a worse failure mode than a number you chose on purpose.

It also will not run on Intel Macs, and it will not offer to sell you manual control on a Mac whose fans it cannot write to. Monitoring is free forever on every supported machine; the $12.99 one-time purchase unlocks manual control on up to 3 Macs. Whether higher fan speeds recover real performance depends on your model and your workload, which is why the temperature readouts cost nothing: you can watch for throttling first and decide afterwards.