Twitcas Comment Custom CSS Tester is a Chrome extension developed by キィー. This free tool falls under the category of Browsers and is specifically listed under the Add-ons & Tools subcategory.

The main purpose of the Twitcas Comment Custom CSS Tester is to allow users to load a custom CSS to the Twitcasting Live Chat Comment overlay. By doing so, users can customize the comment overlay and view it on their web browser. The loaded CSS can also be debugged using the browser's built-in developer tools.

To get started, users need to access the extension's option page to set up and open a comment overlay URL. Once the comment page is opened, the popup page can be used to temporarily edit and hot-reload the custom CSS inserted by this extension.