1. Fiddler is a debugging program for websites.

  2. HTTP proxy / HTTP monitor / Reverse Proxy

  3. Beautiful, cross-platform & open-source tools to debug, test & build with HTTP(S). One-click setup for browsers, servers, CLI tools, scripts and more.

    freemium €6.0 / Monthly (for a Pro subscription)

  4. An modern and intuitive HTTP debugging proxy on macOS & iOS https://proxyman.io

    $49.0 / One-off

  5. HttpMaster is a professional software tool for testing and debugging HTTP applications, primarily aimed at REST API applications and web services.

    freemium

  6. Paw is a REST client for Mac.

  7. Postman is the most efficient way to test, develop and document APIs.

    freemium $8.0 / Monthly (Per user/month billed annually)

  8. 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.

  9. An app to proxy your network connections, native for OS X

  10. Official Twitter account of JMeter, the open source load testing tool by @TheAsf. Code: https://t.co/ADK2A8Pl14. Website: https://t.co/oc0MW2ksea

  11. NetworkMiner is a Network Forensic Analysis Tool (NFAT) for Windows.

  12. Proxy switcher with monitoring and port detection