Title: I built a free desktop tool to intercept, pause, and modify HTTP and WebSocket traffic Hey everyone! I'm a software engineer, and I've been building a side project called Mittelware. The idea started with a problem I encountered while debugging applications. Sometimes, I want to modify an API response, block a URL, simulate an error, or change a request payload without modifying the application or backend code. Browser DevTools already supports URL blocking and response overrides, but I wanted something more sophisticated: a reusable set of rules with flexible matching conditions and the ability to inspect and modify traffic on the fly. I initially built a Chrome extension called Intercept by Mittelware. However, browser extension restrictions made it difficult to implement the level of interception and flexibility I wanted. I also explored existing tools like Requestly and HTTP Toolkit. They are useful tools, but I wanted to build something around my own vision of flexible, rule-based interception, including workflows that go beyond simple request and response overrides. So I decided to build Mittelware as a desktop application. What can Mittelware do? Rule-based interception: Match traffic using URLs, headers, payloads, and other request attributes. Modify HTTP requests and responses: Change content before forwarding requests upstream or returning responses to the application. Block and override requests: Apply custom behavior to matching traffic. Pause traffic on the fly: Inspect a request, modify its content, and then continue processing it. WebSocket message interception: Pause, inspect, and modify WebSocket messages before forwarding them to the upstream connection. Reusable rules: Create and manage rule sets for different debugging and testing scenarios. My goal is to make sophisticated traffic interception and modification accessible to developers without requiring an expensive tool subscription. Mittelware is free to use, and I'd like to keep it accessible while I learn what developers actually need from it. It's still in early beta, and I'm working on stabilizing it before the 1.0 release. 🌐 https://mittelware.com I'd love to hear from fellow developers: How do you currently debug APIs and modify HTTP or WebSocket traffic? Have you encountered limitations with browser DevTools or your current tools? What would you like to see in a rule-based interception tool? Would you find a free desktop tool like this useful? I'm looking for honest feedback and early testers. Suggestions, criticism, and questions are all welcome!   submitted by   /u/arjun2504 [link]   [comments]