[mtlynch]

>The programs you suggested only help to (temporarily) inspect the Request/Response, as you say, but you would need to manually modify the responses every time they come through the proxy, which could easily translate to hundreds of requests per day while using a single app. Surely no one wants to have to sit there modifying every single HTTP request while using an app like Adobe Photoshop.

The tools I mentioned all support rules for automatically modifying requests/responses. Most of them support custom scripting as well.

>Wrong, you still need a custom proxy server for this to work.

Not sure why the rudeness here. I'm just sharing some useful tools that would be easier to use than writing an entire HTTP proxy from scratch.

You'll certainly have more power writing a custom proxy from scratch, but off-the-shelf HTTP proxying tools are a good start for someone exploring this space.