No browser API reports a graphics card's installed memory. A page can only find out how much the browser lets it allocate, by allocating it.
- That amount is smaller than the card's total: the browser and the driver cap what one page may hold, other programs and the desktop already hold some, and memory can be moved out when it is short.
- On an integrated chip, and on Apple silicon, graphics memory is taken from system RAM, so the figure is a share of RAM, not a separate pool.
- The VRAM test grows WebGPU buffers in 256 MiB steps up to a cap you choose, 2 GiB by default, writes a pattern into every word and reads it back. The result is memory allocated and verified, never "your VRAM".
The short answer
As much as the browser allows this page, which the VRAM test measures, and never the whole card. Use the figure to know what a browser app, such as a browser AI runtime or a 3D tool, can rely on here. For the card's installed memory, read the operating system's display settings or the vendor's tool.
We have no recorded runs of this test in our validation notes yet, so this guide quotes no measured results. Every line and constant below is the one the test's code applies.
How the test finds the limit
The page asks WebGPU for storage buffers one step at a time, each 256 MiB or the adapter's buffer limit if smaller, inside error scopes that catch an out-of-memory or a refused buffer. A compute shader fills each buffer with a pattern, another counts every word that differs, and the page checks with 3 patterns. It stops at the cap you chose (1 GiB, 2 GiB, 4 GiB and 8 GiB), or when the browser reported it was out of memory, the browser refused a larger buffer, the browser reset the graphics device and it reached the time limit. The time limit is 60 seconds.
The 2 GiB default is our starting value, chosen so a tab cannot starve the desktop by accident. A run that stops at the cap could have gone further; raise it and run again to find where the browser says no.
Why the figure is not your total
- The browser limits what one page can take, so a single tab cannot take the machine's graphics memory from everything else.
- The desktop, the browser's own drawing and every other open program already hold some of the card's memory.
- The driver can move memory out to system RAM when the card is short, and an allocation that succeeds is not proof it stayed on the card.
- An integrated chip has no memory of its own; the test says so where the adapter makes it clear, as Apple silicon does.
Errors and bandwidth
A healthy card returns every word it was given, so any mismatch fails the run. Errors that repeat at stock clocks point at the card's memory, an overclock or its cooling, as the test's own advice says.
The test then copies between two buffers of 256 MiB each and reports GB/s, the median of 7 runs. Where the adapter offers timestamp queries the copy is timed on the chip; otherwise from the wall clock, which includes the browser's overhead and is labelled so.
Terms used here
Questions
- Can a website read how much VRAM my graphics card has?
- No. WebGPU and WebGL report limits such as the largest buffer, not installed memory. A page learns what it can use only by allocating, which this test does with your permission and a cap.
- Is it safe to allocate graphics memory from a browser?
- The test stops at the cap you set and at the first error, and frees everything when it ends. The browser itself may reset the graphics device if memory runs out, which the result reports.