Postman - The Collaboration Platform for API Development
Insomnia REST - The most intuitive cross-platform REST API Client ð´
soapUI - SoapUI Pro is one of the most prominent API testing platforms around, allowing developers to quickly prototype the functions of their apps and get them to market with little hassle.
Hurl.it - Hurl makes HTTP requests.
Advanced REST Client (ARC) - API testing tool. Which allows web developers to create and test custom HTTP requests.
Cocoa Rest Client - A free open source, native Apple OS X app for testing HTTP/REST endpoints