RESTer is described as 'A REST client for almost any web service (Firefox and Chrome extension)' and is an app in the Web Browsers category. There are more than 25 alternatives to RESTer for a variety of platforms, including Mac, Windows, Linux, Online / Web-based and Chrome OS. The best alternative is Insomnia REST Client, which is both free and Open Source. Other great apps like RESTer are Postman (Freemium), HTTPie (Free, Open Source), Paw (Paid) and Hoppscotch (Free, Open Source).
Rest Client feature rich rest client for developers to debug and test their RESTful web services. It can be used to request a URL using the following HTTP methods: GET, POST, PUT, DELETE, HEAD, PATCH, COPY, SEARCH, OPTIONS.