Charles Proxy - HTTP proxy / HTTP monitor / Reverse Proxy
Web ScrapBook - A browser extension that captures the web page faithfully with highly customizable configurations.
Wireshark - Wireshark is a network protocol analyzer for Unix and Windows. It lets you capture and interactively browse the traffic running on a computer network.
Offline Pages Pro - Offline Pages Pro is probably the world’s most advanced offline browser.
Postman - The Collaboration Platform for API Development
A1 Website Download - Download websites to local disk for offline browsing or preserving a website soon going down.