Find out why your PC slows down.
A free online stress test for your PC, with no download. It measures what it holds under load and names the cause.
The diagnosis
Not how much it slowed. Why. The shape of the curve is the diagnosis, and the report reads it.
A score says the machine got slower. The curve behind it says what happened. Three shapes matter, each with a different cause.
A single step down
A power budget expiring. The machine held its boost for as long as it was allowed to, then dropped to the sustained limit in one move.
A steady slide
Cooling falling behind. Every second under load, a little more is lost, and it does not settle until the fan can keep pace.
A sawtooth
A machine cycling between the two: it cools, boosts, hits the limit, drops, and repeats.
Four stages, then a name for what happened. Does the machine hold what its spec sheet promised, and if not, why not?
Stage 1
Every core, for 60 seconds. The number that matters is the one it settles at.
Parallel Web Workers saturate every logical core and the main thread samples throughput four times a second. Peak arrives in the first second; the rate the machine holds once cooling becomes the limit is what gets reported.
Illustrative run. Your own cores draw their own.
Stage 2
One thread, then six. How much more the memory system gives when asked.
Workers stream 24 MiB arrays to measure bandwidth from one thread and then from all of them, and a pointer chase through a shuffled array measures how long a round trip to memory takes. A machine whose bandwidth barely scales with threads is telling you about its memory channels, not its cores.
One thread
Six threads
Illustrative figures. Not a measurement.
Stage 3
One fixed scene, the same on every card. Frame time, pacing, and how far it falls.
A lit 3D model renders at a fixed 1600 by 900 on a camera path that repeats every ten seconds, and every frame is timed until the graphics chip has finished it. Frames per second, how steadily they arrive, and how far the rate falls are reported. Stutter and slowness look different here, which is the point.
Illustrative frame rates. Not a measurement.
Stage 4
The same scene, soft edges and hard. What realistic shadows cost your card.
The Deep run draws one scene at 1600 by 900 with percentage-closer soft shadows and with plain hard shadows, switching every ten seconds, and times every frame. The gap is the share of frame rate soft shadows take. It is reported, never scored, and the same test runs on its own page.
Illustrative frame rates. Not a measurement.
Stage 5
Samples back to back, each one timed. So the cost of each sample is the measurement.
A WebGL2 path tracer runs samples back to back at a fixed 960 by 540, accumulating each into a float texture, and times every one until the graphics chip has finished it. Samples per second and delivery consistency are reported; a card that delivers unevenly is distinguishable from one that is merely slow.
Illustrative progress. Not a measurement.
Report
Not how much it slowed. Why. The shape of the curve is the diagnosis.
A plateau that steps down once is a power budget expiring. A steady slide is cooling falling behind. A sawtooth is a machine cycling between the two. The report reads the shape, states its confidence, and names the cause with the number to beat on the retest. The next run on the same machine is shown against this one.
Plateau, then a single step down.
Throughput held for 18 seconds, then fell in one transition and stayed there. One fall accounts for 98% of everything the run gave up.
Illustrative shape. Your run draws its own, and the report reads that one.
The limits, stated plainly
What a browser cannot see.
No web page can read a temperature. A cooling-limited machine still shows it, as decay, and decay needs no sensor.
Illustrative shapes. One machine holds near 96% of its peak; one settles at 64%.
Trusted by people who push hardware. Builders, integrators, repair techs.
“I was about to buy a second-hand ThinkPad for 400 quid. Ran the test in the seller's kitchen, watched the CPU stage lose 38 percent in three minutes, and walked away. Best three minutes I spent that week.”
Marcus R. · Buying a used laptop“I hand out one link to clients now instead of a download. They run it, forward me the report, and I know before I drive over whether the cooling is the problem.”
Priya S. · System integrator“My frames were fine for ten minutes and then fell off a cliff every night. The graphics stage showed the same drop at the same point, and the report said thermal ceiling in plain words. New paste, problem gone.”
Devon L. · Gamer, fixed his FPS drops“Exports kept getting slower the longer I worked. I assumed it was the software. The memory stage showed the laptop was fine on mains and lost a third of its speed on battery. Now I edit plugged in.”
Ana M. · Video editor“It says up front what a browser cannot see, and then measures the rest properly. That honesty is why I trust the number it gives me over a spec sheet.”
Tom K. · Sceptical by trade“Forty refurbished desktops in an afternoon, one link each, same test on every machine. The three that graded D all had dust-packed fans. The report told me before the screwdriver did.”
Jordan P. · IT refurbisher“Watching ops per second sink live while the fans spun up taught me more about my machine than any single score ever did. The retest target told me exactly what to aim for after the fix.”
Sana D. · Curious about her own PC“New build, new cooler, and I wanted proof it was worth it. Before and after in two runs: decay went from 31 percent to 6. That is the number I put in the forum post.”
Leo V. · First-time PC builder“Twelve laptops in the classroom, three complaints a week that they were slow. Ran the test on all of them from the same link. Two were throttling badly, ten were fine. Two repairs instead of twelve.”
Ravi N. · School IT admin“I asked in a forum why my new PC felt slower than the reviews said. Someone sent this. Three minutes later I could see it was hitting a power limit under load, and I knew what to change in the BIOS.”
Emily W. · New PC underperforming“Average FPS looked great and the racing still felt wrong. The consistency figure caught frame pacing my overlay was hiding. Once I could see it, I could fix it.”
Chris B. · Sim racer“Customers say slow, I need a number. I run it in the browser while they watch, the report says what is happening in plain words, and the repair conversation is over in a minute.”
Nadia F. · Repair shop ownerEvery part, with its specifications. And what they do not tell you.
1,671 processors and every graphics card we can source properly, with side-by-side comparisons. 101 carry a full sheet today; the rest say “not verified” rather than guess.
Writing
Better as you read. Guides and notes on measuring honestly.
- How path tracing works, from one ray to a finished imagePath tracing follows light backwards from the camera, bouncing at random until it finds a light. How noisy samples become a clean image, and why it costs.
- Path tracing vs ray tracing: what the difference actually isRay tracing in games adds one effect to a normal image. Path tracing computes all the lighting from bounce paths. What each costs, and how to test your card.
- Thermal decay, explainedDecay is the percentage a system's throughput falls from its early peak to its sustained plateau: what it reveals, what it hides, and how to read it.
- What browser benchmarks can and cannot measureThe capability boundary of a web-based benchmark, stated plainly: what the platform exposes, what it refuses to, and where a native tool is the right answer.