Protractor is a free browser add-on developed by ben.burlingham. It is available for the Chrome platform and falls under the category of Browsers, specifically Add-ons & Tools. With Protractor, users can easily measure angles directly in their browser window.

The main feature of Protractor is its ability to move two guides around to accurately match any vertex. This allows users to measure angles with precision. Additionally, Protractor offers customization options such as adjusting precision, units, colors, and more. Users have the flexibility to customize the tool to their preferences.

Protractor also provides additional functionalities like resizing, nudging, locking, and rotating. These features make it easy to manipulate the protractor tool according to specific needs.

For those interested in the technical side, Protractor's code is open source and available on Github.

Overall, Protractor is a convenient and user-friendly tool for measuring angles directly in the browser window. It offers customization options and additional functionalities to enhance the measuring experience.