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.
RESTer - A REST client for almost any web service (Firefox and Chrome extension).
SiteSucker - SiteSucker is a Macintosh application that automatically downloads Web sites from the Internet.