Open-Source HTTP Interceptor & Mocking Tool
Loved by 300k+ developers — intercept, modify, mock, and debug HTTP(S) traffic from your browser and desktop apps.
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Requestly HTTP Interceptor is an open-source HTTP interception and traffic debugging tool that helps developers intercept, inspect, monitor, and modify HTTP(S) traffic directly from browsers and desktop apps.
It supports powerful debugging workflows including request/response modification, API mocking, traffic inspection, and environment overrides without requiring complex proxy or VPN setup.
Trusted by 300,000+ developers and 11,000+ companies worldwide.
Intercept, monitor, and modify HTTP(S) requests and responses in real time.
📚 Docs: https://docs.requestly.com/general/http-interceptor/overview
- Redirect URLs and environments
- Map local files and remote resources
- Modify request and response headers
- Override API request and response bodies
- Inject custom JavaScript into webpages
- Debug and inspect network traffic
- Capture traffic from browsers, mobile apps, and desktop apps
- Redirect production traffic to local or staging
- Test feature flags and edge cases
- Override APIs during frontend development
- Replace analytics or third-party scripts
- Simulate backend failures and latency
Build and test frontend applications without waiting for backend APIs.
📚 Docs: https://docs.requestly.com/general/api-mocking/api-mocking
- Local API mocking
- Cloud-hosted mocks
- Static & dynamic response overrides
- GraphQL request targeting
- Bulk mock generation from sessions
- Mock APIs in Cypress, Playwright, Selenium, and CI pipelines
- Frontend parallel development
- E2E testing
- QA & staging simulations
- Offline development
- Contract testing
Easily migrate existing configurations from other tools.
- Charles Proxy
- ModHeader
- Resource Override
- https://docs.requestly.com/general/imports/charles-proxy
- https://docs.requestly.com/general/imports/modheader
- https://docs.requestly.com/general/imports/resource-override
Pick the install that matches how you work — a lightweight browser extension for in-browser interception, or the desktop app for system-wide traffic capture.
Install Requestly directly into your browser to start intercepting and modifying HTTP(S) traffic in seconds.
| Browser | Download |
|---|---|
| Chrome | Install for Chrome |
| Edge | Install for Edge |
| Firefox | Install for Firefox |
| Safari | Install for Safari |
| Brave / Opera / Vivaldi | Install via Chrome Web Store |
Use the desktop app to capture traffic across browsers, mobile devices, and any desktop application — ideal for debugging, mocking APIs, and sessions.
| Platform | Download |
|---|---|
| macOS (Apple Silicon) | Download for macOS (Apple Silicon) |
| macOS (Intel) | Download for macOS (Intel) |
| Windows | Download for Windows |
| Linux | Download for Linux |
This repository contains the core Requestly platform including:
- Browser Extension
- Web App UI
- Core Traffic Interceptor Logic
Follow the setup guide:
We welcome contributions from the community.
Whether you're fixing bugs, improving docs, or building new features, your contributions help make Requestly better for developers everywhere.
- Explore open issues
- Read the contributing guidelines
- Submit a pull request
- Join the community discussions
- 📚 Documentation: https://docs.requestly.com/general/http-interceptor/overview
- 🔐 Security & Privacy: https://docs.requestly.com/security-privacy/
- 💬 Community: https://get.requestly.com/join-community
- 📧 Email: contact@requestly.com
- ❓ StackOverflow: https://stackoverflow.com/questions/tagged/requestly
Requestly is built to make debugging and testing faster and simpler.
From HTTP interception and API mocking, Requestly gives developers everything needed to debug and ship confidently.