The "Add 'Mark All Read' button to GMail" is a free Chrome extension developed by pressbin. This extension falls under the category of Browsers and is classified as an Add-ons & Tools subcategory.

The main purpose of this extension is to provide users with an easy way to mark all their messages as read in GMail with just one click. With the click of a button, users can change the status of all visible messages from "unread" to "read". This can be particularly useful for users who receive a large number of emails and want to quickly clear their unread messages.

Overall, the "Add 'Mark All Read' button to GMail" extension offers a convenient solution for GMail users who want to efficiently manage their inbox by marking all their messages as read with a single click.