CPU/GPU Stress Test
⚠️ Before you start
- The test pushes your CPU and GPU to full load. Expect loud fans and heat, and faster battery drain on laptops and phones.
- Before you leave a long test (10 minutes, 60 minutes or no limit) unattended, run a short one first to check that everything behaves. If the device gets unusually hot or misbehaves, press Stop immediately.
- Other apps and tabs make the score unstable. For a fair measurement, close them and keep this tab visible while the test runs.
- You use this tool at your own risk. This site is not responsible for hardware failure or data loss.
🖥️ CPU stress test
Runs several Web Workers at once and measures how much work your CPU gets done each second.
✅ Result
🎮 GPU stress test
Draws a Mandelbrot set with a WebGL shader and measures the frame rate (FPS).
✅ Result
About this tool
This tool puts your CPU and GPU under sustained load from the browser and charts how performance changes over time. The CPU test runs a tight arithmetic loop in several Web Workers. The GPU test renders a Mandelbrot set with a WebGL shader. A line chart records the result every second, so a slowdown caused by heat or by power management shows up as a drop in the line.
Everything runs in your browser and nothing is sent to a server.
Where it helps
- Slow-down complaints — a PC that "gets slower the longer I use it": run a 10 to 60 minute test and see whether the line sags. A steady drop points to cooling problems such as dust or dried thermal paste.
- Hangs under load — on an aging machine that freezes when the CPU is busy for a while, a long CPU test shows when the score collapses or stops, which you can compare with the time of the freeze. This can help separate a failing power supply or voltage regulator from a software cause.
- Acceptance checks — run the same test on new, used or leased machines and compare scores between identical models to spot early faults.
- Before and after a repair — run the same settings and duration before and after cleaning, new thermal paste or a fan swap, and compare the charts.
- Battery or power plan — test on AC power and on battery, or under different power settings, to see whether the machine is being held back.
How it works
- CPU score: each worker does arithmetic in a loop and reports how much it finished every 200 ms. The score is the total across workers, scaled to points per second. It is a relative number that depends on the browser and the device.
- GPU score: the frame rate measured between animation frames. The average is the mean of the per-frame rates. The first few frames are skipped. Load sets the iteration count of the shader, and render resolution multiplies the canvas size.
- Slowdown warning: after at least 15 seconds of data, the latest value is compared with the peak (ignoring the first 10% of the run, at least 3 seconds). If it is 15% or more below the peak, a warning is shown.
- The test stops by itself when the chosen time is up, or when you press Stop. The chart and result then cover the time that was recorded. The Stop button also floats at the bottom right while a test is running.
- The slowdown warning is a rough guide only. Other apps, the browser lowering the priority of a hidden tab, or battery saver can cause it too.
FAQ
Q. Why is my score different from someone else’s?
A. The score depends on the browser, operating system and power settings, so it is not comparable between different setups. Use it to compare the same machine over time, or identical machines with the same browser.
Q. Why did the chart stop updating when I switched tabs?
A. Browsers slow down timers and animation in hidden tabs. Keep the tab visible while the test runs, or the readings will be unreliable.
Q. The GPU test says the context was lost.
A. The load was too much for the graphics driver and it reset the GPU. Lower the load or the resolution and try again. The test will work again once the browser restores the GPU.
Q. Is it safe?
A. It is the same kind of load a game or a video encode puts on a machine, but long runs on a hot laptop are not a good idea. Stop at once if the device gets very hot.