What SSD spec sheets print And the one thing none of them do.

First, what this site measures. Neither storage test here benchmarks the drive. The storage test times a file in the browser's private store, which sits on the system drive behind the browser and the operating system's cache. The USB drive speed test times files in a folder you choose. A browser cannot read which drive it is on, its model or its bus. So a figure from either test is the path to the drive, and it is not comparable with the rated speeds below, which a maker measures on the raw drive with a native benchmark.

A QD1 random read is one request at a time, which is the nearest kind of figure to the storage test's random read, though still a raw-drive number. Samsung calls its controller "in-house" without a name; Kingston is the only maker here that names one. A field marked not printed means the document read does not state it; the maker may state it elsewhere. Endurance is printed as TBW, the terabytes a maker warrants the drive to take.

Rated sequential read is the largest "up to" figure the document prints across its capacities. Where a PDF's columns came apart from their labels and a value's place had to be inferred, the figure is not shown here until it is read off the page by hand. Crucial is missing because its site refused every request, and Corsair because only one capacity's page was read for each drive.

Many solid-state drives write first into a fast SLC cache and fall to a slower rate once it is full. No datasheet read here gives the cache's size. The storage test's sustained write mode estimates where it runs out: it writes one stream in 32 MiB chunks for up to 2 minutes, capped at the lesser of 8 GiB and 80% of the space the browser offers, and reports the bytes written before the rate fell below 50% of its first-GiB median and stayed there for 3 chunks. The sustained write guide walks through it.

The USB drive speed test does the same for a drive you choose, in Chrome or Edge on a computer: files of up to 256 MiB written in 1 MiB blocks, with a lasting fall to under 50% of the early speed reported as the cache running out. It also reads every byte back, which finds a drive that reports more space than it has.

Both are estimates through the browser's path, flushes and the system cache included. They show the shape of the fall on your machine; they do not benchmark the drive or check it against its datasheet.