RESTer is a Firefox add-on designed for web development, allowing users to perform a variety of HTTP requests with ease. With support for different methods, URLs, and custom headers, it streamlines the process of testing APIs. Users can save their favorite requests and organize them into collections, making it easy to manage multiple projects. The add-on also features a comprehensive history log that displays full request and response details, enhancing the user experience for developers.

One of RESTer's standout features is its support for Basic and OAuth2 authentication, enabling users to create and store authorization headers. It also allows for the use of placeholders in saved requests and provides shortcuts for frequently used actions. The add-on requires specific permissions to access data for all websites while ensuring that it only inspects its own requests, maintaining user privacy. RESTer is a powerful tool for developers looking to streamline their web development processes.