Mac fan control and temperature monitoring for Apple Silicon
Free and open source. No kernel extension, no SIP changes, no telemetry.
A real run of the control engine — the temperature climbs, the curve maps it, the fan follows.
Beta — 0.1.1. Signed, notarised and installable. It has run on one Mac, a Mac mini (M4, 2024); every other Apple Silicon model should work and none has been tried. Treat it as software under test: keep an eye on temperatures for the first while, and quit Boreas if anything looks wrong — quitting hands the fans back to the firmware immediately. Monitoring alone needs no privileges and changes nothing, which is the safe way to start.
Boreas is a menu bar app that shows what is happening inside your Mac and lets you decide how it should be cooled.
- Read every temperature sensor your Mac exposes — performance and efficiency cores, GPU, memory, storage, power delivery, chassis
- See fan speeds with their real minimum and maximum
- Shape the fan curve yourself with a continuous curve rather than a list of on/off rules, so speed changes are smooth instead of stepped
- Switch profiles automatically based on power source, running app, time of day or thermal pressure
- Record measurements to JSONL or CSV, with a disk ceiling it will not cross
- Get told when something changes — thresholds, thermal pressure, a fan that stops tracking — with noise controls that a panic can still get through
- Wire it into your own tools with a webhook or a script, instead of an email client nobody wants to maintain
- Read it in five languages — English, Turkish, Russian, Spanish and Simplified Chinese
- Stay quiet or stay cool — the trade-off is yours to make, not the firmware's
Beta. Signed and notarised, so it installs without a Gatekeeper detour.
brew tap mahirozdin/boreas
brew trust mahirozdin/boreas # Homebrew asks before running a third-party tap
brew install --cask boreasOr download the signed, notarised .dmg from
the latest release
and verify it against the .sha256 published beside it:
shasum -a 256 -c Boreas-0.1.1.dmg.sha256Building from source works too, and is the only route if you want to change something:
git clone https://github.com/mahirozdin/BoreasMacFanControl.git
cd BoreasMacFanControl
brew bundle # xcodegen, swiftlint, xcbeautify
make generate # produces the Xcode project from project.ymlThen open Boreas.xcodeproj and run. Monitoring works unsigned. Fan control
needs the privileged helper, and macOS will only register a helper signed with a
Developer ID — so a source build needs your own signing identity in
Local.xcconfig (copy Local.xcconfig.example and fill in your team
identifier).
- Open Boreas. It appears in the menu bar and starts reading sensors immediately — no permission, no setup, nothing to configure.
- Pick a profile from the panel: Quiet, Balanced, Performance, or System to hand everything back to the firmware.
- Enable fan control when you want the curve to actually drive the fans. This is the one step that asks for your administrator password, once.
Steps 1 and 2 are useful on their own. Step 3 is optional and reversible.
More of the interface
On Apple Silicon, cooling is entirely firmware controlled and offers no settings. That is a problem in both directions.
Sometimes it is too quiet. During a long compile, a video export or a virtual machine run, the firmware ramps up late and conservatively. The chip throttles, and work that could have finished faster does not.
Sometimes it is too loud. Recording audio, working at night, sitting in a meeting — moments where a few degrees warmer would be a fine trade for silence.
Both come from the same place: the decision is closed to you. Boreas opens it.
| Mac | Apple Silicon — M1 or newer. Intel is out of scope by design |
| macOS | 14.0 Sonoma or newer |
| Disk | A few megabytes |
Boreas is developed on a single machine, so honesty about coverage matters more than a long compatibility table.
| Hardware | Status |
|---|---|
Mac mini (M4, 2024) — Mac16,10 |
Verified on real hardware: 40 named sensors, 1 fan measured from 1000 up to 4021 rpm on an edited curve and handed back on every failure path |
| Every other Apple Silicon Mac | Should work; not verified. Nobody has run it on one |
A note for laptops. Every measurement here comes from a desktop Mac. A MacBook has less thermal headroom and throttles harder, so a curve that is comfortable on a Mac mini may be too quiet on a laptop — and on battery the firmware is more conservative still. Nothing in the design is desktop-specific; it is simply untested there, and a MacBook sensor report would be as useful as any.
What "not verified" means in practice. Sensor naming differs between chip generations, and multi-fan models exercise balancing code that has never met a second fan. Nothing here is theoretical — the mapping is a heuristic over hardware keys, and yours may produce sensors Boreas does not recognise.
If your Mac shows sensors as uncategorized, that is useful information —
Settings → Sensors → Report These Sensors opens a pre-filled
unknown sensor report
in your browser, carrying your Mac's model identifier, chip, the unrecognised
sensor names and the fan count, and nothing else. Unmapped sensors are shown
rather than hidden precisely so they can be reported.
This is the part worth reading before you install anything that touches your fans.
What Boreas asks for
| Permission | When | How often |
|---|---|---|
| Administrator password | Only when you enable fan control | Once |
| Background permission | When the fan helper is registered | Once, in System Settings |
| Notifications | Only if you turn alerts on | Once |
What Boreas never asks for
- ❌ Disabling System Integrity Protection
- ❌ A kernel extension or DriverKit driver
- ❌ Booting into Recovery or changing security policy
- ❌ Full Disk Access
- ❌ Accessibility or Screen Recording
- ❌ Camera, microphone, location, contacts or calendar
Reading temperatures needs no privileges at all. If you never enable fan control, Boreas is a complete monitoring tool that asks for nothing.
Removing the app returns everything to the way it was. No firmware or NVRAM is touched, and fan settings revert to the macOS defaults the moment Boreas stops.
Your session (unprivileged) Root Hardware
┌──────────────────────┐ XPC ┌────────────────┐ IOKit ┌──────────────┐
│ Boreas.app │◀────────▶ │ Fan helper │◀─────▶ │ SMC │
│ control engine │ both │ safety filter │ │ HID sensors │
│ sensor reading ─────┼───────────┼────────────────┼──────▶ │ power source │
│ configuration │ verify │ watchdog │ └──────────────┘
└──────────────────────┘ signature└────────────────┘
Reading temperatures needs no privileges, so it goes straight to the hardware. Only writing fan speeds requires the helper, and the helper's entire surface is four methods: describe the fans, apply targets, hand them back, and a heartbeat.
It reads no configuration, opens no network connection and starts no processes.
The curve is continuous, not a ladder of thresholds. Drag a point, double-click to add one, right-click to remove. The shape cannot be made invalid — edits are clamped rather than rejected, so no sequence of drags produces a curve that falls as it gets hotter. Every edit reaches the fans within a cycle.
Fan control software that gets this wrong damages hardware, so the design puts safety ahead of user preference in five places.
| Layer | Rule | Can it be switched off? |
|---|---|---|
| Fan floor | Never below the hardware minimum | No |
| Thermal state | macOS reports serious → raise; critical → full speed |
No |
| Panic threshold | Any sensor past the limit → full speed, held | No, only lowered |
| Helper guard | Out-of-range commands are refused, not clamped | No |
| Watchdog | No heartbeat → fans handed back to firmware | No |
The watchdog is the one that matters most. If Boreas crashes, hangs, is force quit or you log out, the helper notices the silence and returns control to the firmware on its own. It does not rely on the app to clean up after itself, because the cases that matter are exactly the ones where it cannot.
Every layer can only raise fan speed. None of them can lower it.
What Boreas cannot do: it cannot cool a Mac whose firmware has already stopped the fans, and it cannot exceed the maximum speed the hardware reports. Where the firmware refuses a command, the helper refuses it too rather than retrying.
- No telemetry. No analytics SDK, no crash reporting SDK, no advertising ID
- No network by default. Out of the box, Boreas makes no connections at all. The only code that can open one lives in a single directory, and only runs if you configure a webhook yourself
- Your data stays yours, in files you can read, on your machine
These are not promises about intent. They are checked on every commit by a gate that fails the build if an analytics symbol or an unexpected network call appears.
Everything lives in one file you can read, edit and put under version control:
~/Library/Application Support/Boreas/config.json
{
"schemaVersion": 1,
"general": { "samplingIntervalSeconds": 2 },
"safety": { "panicTemperatureCelsius": 95, "watchdogTimeoutSeconds": 15 },
"profiles": [
{
"name": "Quiet",
"priority": 0,
"binding": {
"input": { "group": "compute", "aggregate": "max" },
"curve": [
{ "celsius": 40, "duty": 0 },
{ "celsius": 58, "duty": 0.15 },
{ "celsius": 72, "duty": 0.4 },
{ "celsius": 82, "duty": 0.7 },
{ "celsius": 88, "duty": 1 }
]
},
"hysteresis": 5,
"smoothing": 0.2,
"slew": { "maxRisePerSecond": 300, "maxFallPerSecond": 100 }
}
]
}That fragment is copied from a real boreas export, not written by hand — a
sample that does not load is worse than no sample.
A broken file can only ever fall back: Boreas keeps running on the last valid
state and leaves the fans with the firmware rather than acting on a document it
does not understand. config.backup.json is refreshed before every write.
Values out of range are clamped, not rejected.
Full schema: schema/config.schema.json ·
Reference: docs/architecture/configuration.md
boreas does everything the menu bar can, on a machine with no window server:
boreas status temperatures, fans and power at a glance
boreas sensors [--raw] every sensor, grouped; --raw shows hardware names
boreas profile [name] list profiles, or activate one now
boreas profile --auto hand the decision back to the profile triggers
boreas install install the fan control helper
boreas uninstall [--all] remove the helper; --all also deletes saved settings
boreas export [file] write the configuration; stdout when no file is given
boreas import <file> replace the configuration, after validating it
$ boreas status
power : adapter
sensors : 40 hottest PMU Die 1 75.1 C
fan 0 : Fan 1 1000 rpm (1000-4900, 0%)
control : enabledA profile chosen from the command line is live only and never written to disk — a stored choice would override every profile trigger for good.
Some of what looks like a fault is a safety guarantee doing its job, so the short version is worth having in front of you:
| What you see | Most likely reason |
|---|---|
| Fan speeds never change | Fan control is not enabled — reading needs no privileges, writing needs the helper. Without it Boreas is a monitor and shows no error, by design |
| Helper stuck "waiting for approval" | macOS owns the second step: System Settings → General → Login Items & Extensions |
| The profile never switches by itself | A manual choice outranks every trigger and does not expire unless you gave it a time limit. boreas profile --auto hands the decision back |
| Speeds revert on their own | The watchdog. On quit, crash, sleep or log out the fans go back to the firmware unconditionally — that is the feature, not a bug |
| Fans pinned at full speed | The panic threshold or the macOS thermal state. Both release on their own; neither can be switched off |
| Sensors show as uncategorised | Sensor keys are opaque codes and unmapped ones are shown rather than hidden, so they can be reported |
| No notifications | Nothing is requested until you turn alerts on, and a refusal turns the switch back off |
| A setting did not stick | A profile chosen from the CLI is live only, on purpose. A broken config file falls back to the last valid state |
Full detail, including what to collect before opening an issue:
docs/operations/troubleshooting.md.
boreas uninstall --allThat removes the privileged helper and deletes
~/Library/Application Support/Boreas. Then drag the app to the Trash.
Without --all the helper is removed and your settings are kept. Either way:
- The fans go back to the firmware immediately — the helper hands them over as it stops, and the watchdog would do it anyway
- No firmware setting, NVRAM variable or system file is touched, because none was ever written
- Nothing is left in
LaunchDaemons, andlaunchctlno longer knows the service
This was verified from five angles rather than assumed — SMAppService status,
launchctl, the system folders, the deleted support directory and the absent
process. It is not re-checked automatically: install and uninstall change
the helper's registration and prompt for a password, so the command line test
suite deliberately exercises everything except those two.
| Phase | Status |
|---|---|
| Documentation system and gates | ✅ Done |
| Toolchain and project scaffold | ✅ Done |
| Sensor and fan reading | ✅ Done |
| Privileged helper and XPC | ✅ Done |
| Fan control and safety chain | ✅ Done |
| Control engine — curves, hysteresis, profiles | ✅ Done |
| User interface and curve editor | ✅ Done (a VoiceOver pass is outstanding) |
| Notifications, logging, diagnostics, CLI, automation | ✅ Done |
| Signing, notarisation, release | ✅ Done — 0.1.1 is signed, notarised and published as a beta |
Later, and deliberately not before 1.0: a WidgetKit widget, App Intents, a local metrics endpoint, configuration sharing, and in-app updates.
Current status and next task: TODO.md.
Why is my Mac running hot? Usually sustained load — compiling, exporting video, running virtual machines. On a MacBook, a warm room or a blocked vent turns the same load into throttling sooner. Boreas shows you which part of the chip is hot, so you can tell a busy CPU from a cooling problem.
Can you control fan speed on Apple Silicon Macs? Yes, through the System Management Controller, with a small privileged helper. Boreas asks for an administrator password once and never needs one again.
Does this need SIP disabled or a kernel extension? No. Neither. That is the main reason this project exists in the shape it does.
Is it safe to lower fan speeds? Lowering them raises thermal risk, which is why five safety layers can only ever raise the speed, and three of them cannot be switched off.
What happens if the app crashes? The helper stops receiving heartbeats and hands the fans back to the firmware within seconds. This is tested, not assumed.
Will it work on my Intel Mac? No. Intel Macs use a different sensor and SMC layout, and supporting both would double a code base maintained by one person.
Can it email me when my Mac gets hot?
Not directly, and that is deliberate. A webhook or a one-line script can, and
neither makes this project responsible for storing your mail password — there is
a ready-made example in
docs/operations/notifications.md.
Bug reports, hardware reports and translation fixes are all welcome. Please read
CONTRIBUTING.md first — it covers the setup, the workflow,
and the rules this project enforces on itself.
The most useful thing you can contribute right now is a sensor report from a
Mac that is not an M4 mini. Three of the five interface languages have not been
read by a native speaker either, and
TRANSLATORS.md says exactly which.
make next # tells you which task is next
make check # runs every gate — must be green before pushing
make test # Swift package tests
make smoke # hardware smoke test on a real MacThis repository uses a document driven workflow with machine enforced rules.
Start at BOOT.md, then AGENTS.md, then
TODO.md. Setup and the application's own diagnostic commands:
docs/development/setup.md.
Boreas is provided as is, without warranty of any kind. Lowering fan speeds increases thermal risk, and the responsibility for that is yours. Any effect on your hardware warranty is likewise yours. This project is not affiliated with, authorised by or endorsed by Apple Inc.
Apache-2.0. Attributions and trademark notices: NOTICE.