How to use the CPU stress test
- Start test: Starts one worker for every processor thread, warms up for 5 seconds, then measures for 5 seconds and shows a score. Press Stop at any time; a run stopped early doesn't get a score.
- Keep running until I stop it: Turn this on to keep every thread busy until you press Stop. The score then shows the last 5 seconds, so you can watch how your CPU holds up over several minutes.
- Processor: How many threads your browser reports. The test uses all of them.
- Speed over time: The work completed each second, in points per second. A flat line means steady performance; a falling line means the CPU is slowing down.
- Comparison bar: Places your score in one of four rough bands, from Basic (older laptops and budget phones) to Very fast (high-end desktops). It's a guide, not a precise ranking: the bands are anchored on a measured 12-thread desktop scoring about 4,900, with other devices estimated from it.
The score is specific to this test and best for comparing runs on the same device and browser.
Diagnosing CPU and system problems
- System crashes or freezes: If the device crashes, freezes, or reboots under load, suspect overheating, an unstable overclock, an insufficient power supply, or failing hardware (CPU, RAM, or motherboard).
- Thermal throttling: With the test set to keep running, a speed that starts high and then drops and stays low means the CPU is reducing its speed to cope with heat. Excessive throttling points to inadequate cooling. Use a monitoring app alongside the test to see actual temperatures.
- Fan noise and behavior: Listen to the fans. Very loud fans, fans that don't spin up, or unusual noises can mean cooling problems.
- Excessive heat: If the device becomes unusually hot to the touch, the cooling may be struggling even if it doesn't throttle or crash right away.
- Rapid battery drain: Fast drain is expected under full load, but extremely fast drain can be a sign of a worn battery.
- Working device: The test runs without crashes, the speed stays steady, and the fans speed up but temperatures stay within safe limits.
- Malfunctioning device: Freezes, crashes, or reboots, a speed that falls sharply as the CPU heats up, or excessive heat.
Common Issues & Fixes
The score is lower than expected or keeps dropping
- Power mode: Plug in your laptop and choose a high-performance power mode. Battery-saver modes limit CPU speed.
- Background apps: Close other programs and browser tabs; they compete for the same threads.
- Cooling: Clean dust from fans and vents, and use the device on a hard surface so air can flow.
- Thermal paste: On older desktops and laptops, dried-out thermal paste is a common cause of throttling.
The browser or device becomes unresponsive
- Expected under load: Using every thread can make other apps sluggish. Press Stop, or close the tab, to end the test.
- Crashes: If the whole device crashes or restarts, stop testing and check cooling and power before running it again.
Always make sure your device has good ventilation when running stress tests, especially laptops and compact devices. This browser-based test gives you a quick, accessible baseline; for precise temperatures and long burn-in tests, use a dedicated native app.
Frequently asked questions
Why does the score vary between runs?
Background apps, temperature, and power settings all affect sustained performance. Run the test a few times and compare the typical result.
Is it safe to run a CPU stress test?
Yes, for a healthy device. Modern CPUs slow themselves down before they overheat. Save your work first and stop if the device gets unusually hot.