Requestly — Open-Source API Client and HTTP Interceptor

Introduction

Requestly is an open-source API development and debugging platform. It combines an API client for crafting HTTP requests with powerful traffic interception rules that let developers redirect URLs, modify headers, inject scripts, and mock API responses directly in the browser or desktop app.

What Requestly Does

• Sends and tests HTTP/REST, GraphQL, gRPC, and WebSocket requests from an integrated client
• Intercepts and modifies live network traffic using declarative rules (redirect, modify headers, throttle)
• Creates mock API endpoints that return predefined responses for frontend development
• Records and replays browser sessions for debugging and sharing reproduction steps
• Syncs rules and collections across teams via Git-based collaboration

Architecture Overview

Requestly consists of a browser extension that hooks into the browser's webRequest API for traffic interception, and a standalone desktop application built with Electron for system-level proxy capabilities. The API client component uses a React-based UI with support for environment variables, pre-request scripts, and response assertions. Team collaboration features use a cloud backend for sync.

Self-Hosting & Configuration

• Install the browser extension for quick rule-based HTTP interception
• Download the desktop app for full proxy capabilities and system-wide interception
• Clone the open-source repository and run locally for development or self-hosted use
• Configure rules via the visual rule builder or import/export JSON rule files
• Set up team workspaces for shared rules and mock endpoints

Key Features

• Visual rule builder for creating HTTP modification rules without code
• API client with support for REST, GraphQL, gRPC, and WebSocket protocols
• Session recording that captures network activity for bug reproduction
• Mock server for simulating API responses during frontend development
• Git-sync for version-controlling rules and API collections

Comparison with Similar Tools

• Postman — established API client with larger ecosystem; Requestly adds traffic interception
• Insomnia — REST/GraphQL client; Requestly combines API testing with live traffic modification
• Charles Proxy — system-level HTTP proxy; Requestly works at the browser level with a simpler UI
• mitmproxy — powerful CLI proxy for advanced users; Requestly offers a visual rule-based approach
• Bruno — offline-first API client; Requestly adds interception and session recording features

FAQ

Q: Is Requestly fully open source? A: The core platform and browser extension are open source. Some team collaboration features are available in the cloud-hosted version.

Q: Can I use Requestly to mock APIs for frontend development? A: Yes. Create mock endpoints that return predefined JSON responses and use them during local development.

Q: Does it work with HTTPS traffic? A: Yes. The browser extension handles HTTPS natively. The desktop app uses a local proxy with certificate installation.

Q: Can I share rules with my team? A: Yes. Export rules as JSON files or use team workspaces for real-time sync.

Sources

• https://github.com/requestly/requestly
• https://requestly.com