A macOS menu bar app that monitors thermal pressure and alerts you when your Mac is being throttled.
- Displays thermal pressure state in the menu bar using different thermometer icons
- Shows CPU core temperature (reads directly from SMC)
- History graph showing thermal state and temperature over the last 10 minutes
- Statistics showing time spent in each thermal state
- Configurable notifications:
- When heavy throttling begins
- When critical throttling occurs
- When throttling stops (recovery)
- Optional notification sounds
- Launch at Login option
- No helper daemon or admin privileges required
| Icon | State | Description |
|---|---|---|
thermometer.low |
Nominal | Normal operation |
thermometer.medium |
Moderate | Elevated thermal pressure |
thermometer.high |
Heavy | Active throttling |
thermometer.sun.fill |
Critical | Severe throttling |
- Download the latest
.dmgfrom Releases - Drag
MacThrottle.appto your Applications folder - Right-click the app → "Open" → "Open" (required for unsigned apps)
Building locally automatically signs the app with your development certificate, avoiding Gatekeeper issues.
# Clone the repo
git clone https://github.com/angristan/MacThrottle.git
cd MacThrottle
# Build with Xcode
xcodebuild -project MacThrottle.xcodeproj \
-scheme MacThrottle \
-configuration Release \
-derivedDataPath build
# Run the app
open build/Build/Products/Release/MacThrottle.appOr open MacThrottle.xcodeproj in Xcode and press Cmd+R to build and run.
MacThrottle reads thermal pressure using the Darwin notification system (notify_get_state), specifically the com.apple.system.thermalpressurelevel notification. The system reports 5 levels (nominal, moderate, heavy, trapping, sleeping), but MacThrottle consolidates the last two into "critical" since they're rarely reached in practice. Heavy is where throttling really kicks in.
Note: This notification name is not publicly documented by Apple. It comes from the private
OSThermalNotification.hheader (askOSThermalNotificationPressureLevelName) and has been available since macOS 10.10. See Thermals and macOS for more details on macOS thermal APIs. You can see it implemented in Bazel for example.
macOS provides ProcessInfo.thermalState as a public API, but it has limited granularity (only 4 states vs the 5 actual pressure levels):
ProcessInfo.thermalState |
Actual Pressure Level |
|---|---|
| nominal | nominal |
| fair | moderate |
| fair | heavy |
| serious | trapping |
| critical | sleeping |
The moderate and heavy states both map to fair in ProcessInfo.thermalState, but the difference is significant: heavy is when throttling really kicks in. MacThrottle provides this granularity.
MacThrottle displays CPU temperature alongside thermal pressure using two methods:
The System Management Controller (SMC) is a hardware chip in every Mac that manages thermal sensors, fans, and power. MacThrottle reads directly from the SMC via IOKit to get actual CPU core temperatures.
- Reads chip-specific sensor keys (different for M1, M2, M3)
- Provides accurate per-core temperature readings
- Based on the approach used by Stats
If SMC reading fails, MacThrottle falls back to the IOHIDEventSystem private API:
- Reads temperature events from PMU (Power Management Unit) sensors
- Simpler but less granular: returns aggregate "tdie" temperatures rather than per-core values
- May report slightly different (typically lower) values than SMC
The displayed temperature is the maximum reading across all available CPU sensors.
- macOS 26.0+ (Tahoe)