HttpMaster is described as 'professional development and test tool for web applications, with special focus on REST web services and web API applications' and is a HTTP Client in the Development category. There are more than 25 alternatives to HttpMaster for a variety of platforms, including Windows, Mac, Linux, Online / Web-based and SaaS. The best alternative is Insomnia REST Client, which is both free and Open Source. Other great apps like HttpMaster are Postman (Freemium), cURL (Free, Open Source), Fiddler (Freemium) and Hoppscotch (Free, Open Source).
Postman is a tool that facilitates the development and use of APIs. Postman provides all the functionality needed to create or simulate API specifications and use the Postman Collection Runner to create tests.
cURL is a computer software project providing a library and command-line tool for transferring data using various protocols with URL syntax: supporting FTP, FTPS, SCP, SFTP, HTTP, HTTPS, TFTP, TELNET, DICT, LDAP, LDAPS and FILE.
Fiddler is a Web Debugging Proxy which logs all HTTP(S) traffic between your computer and the Internet. Fiddler allows you to inspect all HTTP(S) traffic, set breakpoints, and "fiddle" with incoming or outgoing data.