Restfox is a free and open-source, somewhat minimalist, HTTP (and socket) testing client. It's available in both desktop and web forms, and it works on all major OSes out there such as Linux, Windows, and macOS.

At its core, Restfox is a beginner-friendly, streamlined HTTP client that does exactly what other apps of this type do - provide its users with a simple way to test and interact with RESTful APIs.

In short, it's good for creating HTTP requests, viewing responses, and managing API endpoints.

Since Restfox wasn't designed to be a hardcore, full-featured HTTP client, the GUI is also quite simple and conventional. Considering that REST APIs are a somewhat unique type of API (usually found in cloud apps), the whole app is centered around this fact.

There are three main GUI sections: a workspace panel on the left, a functions panel in the middle, and, of course, a preview panel on the right.

There's also a minimalist toolbar at the top of the GUI and it's the place from where users can quickly change the GUI themes and views, access the import and export sections, as well as the Settings menu, see logs, and manage the plugins.

Even though it's designed to be a simple app, Restfox offers plugin support. Plugins can be used by more experienced developers to tweak the request data before a request is sent, as well as adjust the response data after a response is received.

More information about the plugins and how to get the most out of them is available on the app's official website.  The website is also the place where you can access the web version of Restfox if that suits your fancy.