The same tool as the browser workbench, installed. Two things change, and they are the only reasons to prefer it.
Your work is yours. The browser version keeps your products and verdicts in that browser's storage, which a cleared cache or a new laptop takes with it. The desktop app keeps them in a database on your machine.
It works offline. The catalog is fetched once rather than on every visit.
Download for Windows Or use it in the browser
Version 0.6.0 · 90 MB · Windows 10 or 11, 64-bit. Installs for you alone, so Windows will not ask for an administrator.
You will see a blue "Windows protected your PC" screen. Choose More info, then Run anyway.
This is not a sign that something is wrong with the file, and it is not something you should take on trust either. SmartScreen shows that warning for any installer it has not yet seen enough copies of; a code-signing certificate is what shortens it, and ProveSpec does not have one yet. If you would rather not click through a warning, the browser workbench is the same tool and needs no install.
In PowerShell, from wherever the file landed:
Get-FileHash 'ProveSpec Setup 0.6.0.exe' -Algorithm SHA256SHA-256 5632d800d3f5f4b848735b239e1c3e941e6583d1444bba014d4a8570a1f99f78
macOS and Linux are not built yet. The packaging covers them, but nobody has produced or tested a build, and publishing one nobody has run would be a guess dressed as a release. Say so on the releases page if you want one.