It measures various performance characteristics and capabilities of the hardware it is running on and reports them as a Windows Experience Index (WEI) score.

For example, a computer with the lowest subscore being its memory, would benefit more from a RAM upgrade than adding a faster hard drive (or any other component).

[2] Detailed raw performance information, like actual disk bandwidth, can be obtained by invoking winsat from the command line.

[8] Obtaining the WEI score from the command line is done invoking winsat formal, which also updates the value stored in %systemroot%\Performance\WinSAT\DataStore.

[10]) The WEI is also available to applications through an API, so they can configure themselves as a function of hardware performance, taking advantage of its capabilities without becoming unacceptably slow.

[12] According to an article in PC Pro, Microsoft removed the WinSAT GUI in order to promote the idea that all kinds of hardware run Windows 8 equally well.