Checkmate - Verified Twitter is a free Chrome extension developed by Inti De Ceukelaire. It falls under the category of Browsers and specifically the subcategory of Add-ons & Tools. This extension allows users to see who is verified on Twitter for no cost at all.

The main feature of Checkmate - Verified Twitter is that it adds back the blue check mark for all verified Twitter users. This feature is based on the last snapshot taken on November 1, 2022. If the extension detects that a blue check mark has been removed from a verified user, it automatically adds it back.

It's important to note that this extension will only have visible effects if verified badges are actually being revoked by Twitter. Currently, as long as Elon Musk has not started revoking verified badges, the extension may not have any visible impact.