Storage. What the browser's file path delivers.
A 64 MiB file written, flushed, read back and read 2,000 times at random inside the browser's private file store, timed in a worker around each call alone. It measures the browser's storage path, not the drive directly.
An illustration of the path, not a measurement. The test reports your own figures.
File
64 MiB, deleted after
Sequential
16 chunks of 4 MiB
Random
2,000 reads of 4 KiB
Store
Origin Private File System
Run it
The storage test. A few seconds, in this tab.
Writes and reads a 64 MiB file in the browser's private store, then deletes it. A few seconds.
What you will get
Sequential write and read speed in MB/s and random 4 KiB reads per second, through the browser’s sandboxed storage. Nothing is uploaded, and the file is deleted when the test ends.
One file, four steps, then gone.
A web page cannot open your drive. What it can do is write a file into a store the browser keeps for this site, and time how fast that path is. That is what an app in the browser gets, and it is a real figure, but it is not the drive's rated speed and the page does not pretend it is.
- A synchronous handle in a worker
- The Origin Private File System gives a worker a synchronous access handle: a real write and a real read that return when they are done. The page drives the worker one step at a time, and each step is timed inside the worker around the call alone, so message hops are not in any figure.
- Write, then flush
- 16 chunks of 4 MiB, filled with a fixed pseudo-random pattern so a store that shortcuts empty pages cannot make the write look free, then one flush. The flush is inside the write figure, because until it returns the bytes may still be in a buffer, and its own time is shown beside it.
- Read back, then read at random
- The same 16 chunks read in order, then 2,000 reads of 4 KiB at offsets from a fixed-seed generator, so every run reads the same places. A read this soon after the write is likely served from a cache, and the result says so.
- Deleted
- The file is removed at the end of the run, and again at the start of the next one in case a run was interrupted. Nothing is requested from the browser's quota; if the browser refuses the space, the result says so and does not retry.
Three figures, with their spread.
No score. Megabytes are decimal, one million bytes, the way drive makers quote them.
Sequential write
64 MiB over the sum of the chunk times plus the flush, in MB/s. The spread of the per-chunk rates is shown beside it: a cache filling part way through, or another program on the disk, shows as a large spread.
Sequential read
64 MiB over the sum of the chunk times, in MB/s, with the same spread. Higher than the write on most machines, and often higher than the drive alone, because the bytes just written are still cached.
Random read
2,000 reads of 4 KiB per second (IOPS), and the mean microseconds per read. This is the figure that separates a solid-state drive from a spinning one, and a browser path with a per-call cost from one without.
Flags
If the tab was hidden for more than a second, the driver waited between steps and the result says so. A browser without a synchronous handle reports not supported rather than a slow figure.
An illustration of the path, not a measurement. The test reports your own figures.
Hardware
What it needs. Three tiers, no fine print.
Minimum
Chrome, Edge or Firefox
Any current version; Safari 17 or later. Older Safari and older Firefox have no synchronous handle and report not supported.
Recommended
Some free space, other downloads finished
The file is 64 MiB. A download or a sync client writing at the same time shares the path.
Optimal
Run it twice
The second run reads a file the first one already touched; if the two runs disagree, the difference is the cache.
Questions
Storage, answered
- Is this my SSD's speed?
- Not directly. The test measures the browser's storage path: the Origin Private File System, which sits on the drive but behind the browser's own layer and the operating system's cache. On a fast drive the path is usually the limit, so the figure says what a web app can get here, not what the drive is rated for. A native tool such as CrystalDiskMark or Blackmagic Disk Speed Test reads the drive itself.
- What is the Origin Private File System?
- A private store the browser keeps for each site, invisible to other sites and to your file manager. This page writes one file there, times it, and deletes it. Nothing is written anywhere you can see, and nothing is uploaded.
- Why is the read so much faster than the write?
- Because the bytes were just written. The browser or the operating system still holds them in memory, so the read back is served from a cache more often than from the drive. The result says so rather than presenting it as the drive's read speed.
- Why does it say not supported?
- The synchronous access handle the test needs exists in Chrome, Edge and Firefox, and in Safari from version 17. An older browser has no path that measures anything honest, so the page reports not supported instead of a made-up figure.
- Is this part of the main SystemCheck run?
- No. It runs on this page only, on its own, and it does not change the score or the report.