Postman - The Collaboration Platform for API Development
Insomnia REST - The most intuitive cross-platform REST API Client ð´
RESTClient - RESTClient can be used to test variety of HTTP communications and RESTful webservices.
Postwoman - An online, open source API request builder
Advanced REST Client (ARC) - API testing tool. Which allows web developers to create and test custom HTTP requests.
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.