Free Browser Stress Test
Put a steady load on your PC from the browser: every CPU thread, a heavy GPU shader and a memory fill, with live graphs. Nothing to install, nothing uploaded, and Stop All is always one click away.
Free, no account. Works in current versions of Edge, Chrome and Firefox; the compute test needs WebGPU.
Honest Numbers
StressTest runs inside your browser, so it measures what the browser can do on your PC. That makes it good for comparing runs on the same PC and browser, and for checking that a PC stays stable under load. It is not a native benchmark, and it gives no score.
| Test | What it reports | Keep in mind |
|---|---|---|
| CPU | Work rate in iterations per second, per thread and in total; how many times one thread’s rate all threads deliver; how late the page’s own timer runs under load. | The tests run JavaScript, not native code. Clock speeds drop as more cores work, and SMT (Hyper-Threading) siblings share a core, so scaling below the thread count is normal. |
| GPU render | Frames per second, frame times and shaded pixels per second from a WebGL2 shader. | The display refresh rate caps the frame rate; Auto intensity adds work until the GPU sets the pace. The browser picks the GPU, which may be the integrated one on a laptop. |
| GPU compute | Billions of floating-point operations per second (GFLOP/s) from 1024 x 1024 matrix multiplies. | Needs WebGPU. The figure includes the browser’s own overhead. |
| Memory | How fast the browser can allocate and commit memory, and read, write and copy bandwidth. | A browser tab can use far less memory than the PC has, so a fill can stop at the tab’s limit. |
| Timing | Frame pacing, timer precision, and the time from a pointer move to the next frame. | These measure the browser’s timing on your PC, not the hardware alone. |
Compare runs on the same PC in the same browser: before and after a BIOS or driver update, a new power plan, a cooler, or a Process Lasso rule. Numbers from different browsers, and from native benchmarks, are not comparable.
Experiments
StressTest gives you a repeatable load. Process Lasso changes how Windows runs it. Together they show what a setting really does.
Run the Thread Scaling preset, then give your browser a CPU affinity rule in Process Lasso, for example only the P-cores of a hybrid CPU, and run it again. The CPU Affinity Calculator builds the mask.
Run All Cores with Process Lasso’s Performance Mode on and off, or under different power plans, and compare the work rates and how steady they stay.
Process Lasso’s graph and process list show the browser’s CPU and memory use as each test runs. By default, ProBalance leaves the app you are using alone; for a guided demo of ProBalance, use CPUEater in Process Lasso’s Tools menu.
Questions
It uses only what any web page may use, and the browser keeps it in check. Like any stress test, a sustained load raises temperatures and fan speeds, so stop it if the PC overheats or throttles. Nothing starts until you press Start, every run stops after 10 minutes at most, and everything stops when you hide the tab.
No. Everything runs in your browser and nothing is uploaded. The page keeps only your last settings, in your browser’s local storage.
Browsers draw in step with the display. Choose Auto intensity: It adds work until the GPU, not the display, sets the pace, and the shaded pixels per second figure shows the throughput.
Browsers limit how much memory one tab can use, often to a few gigabytes. When the fill reaches that limit, StressTest says so and keeps what it has. That is the tab’s limit, not the PC’s.
The tests run as JavaScript, WebGL and WebGPU inside the browser’s sandbox, with the browser’s own overhead. Use them to compare runs on the same PC and browser.
Each browser has its own JavaScript engine and graphics layer. Compare results from the same browser.
Browsers slow hidden tabs, so results from a hidden tab are not meaningful. StressTest stops every test when its tab is hidden; keep it in front while it runs.
Bitsum Technologies
Independent Windows software since 2002. We build novel solutions to software performance and automation challenges.