Postman - The Collaboration Platform for API Development
HTTrack - HTTrack is a free (GPL, libre/free software) and easy-to-use offline browser utility.
Insomnia REST - The most intuitive cross-platform REST API Client ð´
WebCopy - Cyotek WebCopy is a free tool for copying full or partial websites locally onto your harddisk for offline viewing.
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.
SiteSucker - SiteSucker is a Macintosh application that automatically downloads Web sites from the Internet.