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# 🚀 What is Requestly HTTP Interceptor?
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**.
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## ✨ Features
### 🌐 HTTP Interceptor
Intercept, monitor, and modify HTTP(S) requests and responses in real time.
📚 Docs: https://docs.requestly.com/general/http-interceptor/overview
#### Supported capabilities
- 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
#### Common use cases
- 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
### ⚡ API Mocking
Build and test frontend applications without waiting for backend APIs.
📚 Docs: https://docs.requestly.com/general/api-mocking/api-mocking
#### Features
- 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
#### Supported workflows
- Frontend parallel development
- E2E testing
- QA & staging simulations
- Offline development
- Contract testing
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## 🏁 Getting Started
### Install Requestly HTTP Interceptor
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.
#### 🌐 Browser Extension
Install Requestly directly into your browser to start intercepting and modifying HTTP(S) traffic in seconds.
| Browser | Download |
| --- | --- |
| Chrome | [Install for Chrome](https://get.requestly.com/chrome-store) |
| Edge | [Install for Edge](https://get.requestly.com/microsoft-edge) |
| Firefox | [Install for Firefox](https://get.requestly.com/firefox) |
| Safari | [Install for Safari](https://get.requestly.com/safari) |
| Brave / Opera / Vivaldi | [Install via Chrome Web Store](https://get.requestly.com/chrome-store) |
#### 🖥️ Desktop App
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)](https://get.requestly.com/macOS) |
| macOS (Intel) | [Download for macOS (Intel)](https://get.requestly.com/macOS-Intel) |
| Windows | [Download for Windows](https://get.requestly.com/windows) |
| Linux | [Download for Linux](https://get.requestly.com/linux) |
> The desktop app source code lives in a separate repo: [requestly/http-interceptor-desktop-app](https://github.com/requestly/http-interceptor-desktop-app).
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## 🧑💻 Development
This repository contains:
- **Browser Extension** (`browser-extension/`) — Chrome, Firefox, Edge (Manifest V3)
- **Web App UI** (`app/`) — the dashboard at [app.requestly.com](https://app.requestly.com)
- **Core Traffic Interceptor Logic**
### Local Setup
Follow the setup guide:
👉 [Getting Started](./getting-started.md)
### Related Repositories
- [Desktop App](https://github.com/requestly/http-interceptor-desktop-app) — Electron shell for system-wide interception
- [Mock Server](https://github.com/requestly/requestly-mock-server)
- [Web SDK](https://github.com/requestly/requestly-web-sdk)
- [Proxy Engine](https://github.com/requestly/requestly-proxy)
- [Automation integrations](https://github.com/requestly/requestly-automation) — Selenium / Playwright / Puppeteer
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## 🤝 Contributing
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.
### How to contribute
1. Explore open issues
2. Read the contributing guidelines
3. Submit a pull request
4. Join the community discussions
### Useful links
- [Issues](https://github.com/requestly/interceptor/issues)
- [Contributing Guide](./CONTRIBUTING.md)
- [Community](https://get.requestly.com/join-community)
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## 🛟 Support & Resources
- 📚 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
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## A note on this repository
The open-source source code for the Requestly HTTP Interceptor extension and web app lives here at `requestly/interceptor`. Previously this code lived under `requestly/requestly`; that URL is now the community and issue tracker for the [Requestly API Client](https://github.com/requestly/requestly).
The HTTP Interceptor remains fully open source and actively maintained. Contributions, bug reports, and feature requests are welcome here.
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## ❤️ Built for Developers
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.
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### Deferred / TODO before publishing
- [ ] Brand asset paths (`https://github.com/requestly/interceptor/blob/master/app/src/assets/img/brand/...`) — verify these files exist in the new repo after the codebase migration
- [ ] Screenshot URLs (currently `github.com/user-attachments/...`) — verify they remain accessible from the new repo context (user-attachments are organization-scoped, should be fine)
- [ ] Decide whether to keep `discussions` link (current README has it; some teams disable Discussions to reduce triage surface)
