HAR Proxy

A CLI tool that parses HAR (HTTP Archive) files and creates a RESTful mock server. Perfect for API mocking, testing, and development without backend dependencies.

Installation

# Using npm
npm install -g har-proxy

# Using pnpm
pnpm add -g har-proxy

# Or run directly with npx
npx har-proxy <har-file>

Requirements

• Node.js >= 18.0.0

Usage

har-proxy <har-file> [options]

Options

| Option | Description | Default | |--------|-------------|---------| | -p, --port <number> | Port to run the server on | 3000 | | --no-cors | Disable automatic CORS header injection | CORS enabled | | -V, --version | Output the version number | - | | -h, --help | Display help information | - |

Examples

# Start server with default port (3000)
har-proxy recording.har

# Start server on custom port
har-proxy recording.har --port 8080
har-proxy recording.har -p 8080

# Disable automatic CORS headers (use original HAR CORS headers)
har-proxy recording.har --no-cors

CORS Support

By default, har-proxy automatically adds CORS headers to all responses, allowing cross-origin requests from any domain:

• Access-Control-Allow-Origin: *
• Access-Control-Allow-Methods: GET, POST, PUT, DELETE, PATCH, OPTIONS
• Access-Control-Allow-Headers: Content-Type, Authorization, X-Requested-With

The server also handles preflight OPTIONS requests automatically.

Note: If your HAR file already contains CORS headers, har-proxy will preserve them and not add duplicates.

Disabling CORS

Use --no-cors when:

• You need to test CORS behavior with specific origins
• Your frontend handles CORS differently

har-proxy recording.har --no-cors

When CORS is disabled, any CORS headers present in the original HAR recording will be preserved.

Important: Proxy Path

All HAR-recorded endpoints are served under the /proxy path prefix.

For example, if your HAR file contains a request to /api/users, it will be available at:

http://localhost:3000/proxy/api/users

This design separates HAR endpoints from internal routes (dashboard, health checks, etc.).

Path Mapping Examples

| Original HAR Path | Proxy Server Path | |-------------------|-------------------| | /api/users | /proxy/api/users | | /api/products/123 | /proxy/api/products/123 | | /v1/auth/login | /proxy/v1/auth/login |

Query Parameters

Query parameters in requests are automatically stripped for matching purposes. This means:

# Both of these will match the same HAR entry for GET /api/users
curl http://localhost:3000/proxy/api/users
curl http://localhost:3000/proxy/api/users?page=1&limit=10

This allows flexible testing without needing exact query parameter matches.

Dashboard

After starting the server, a web dashboard is available at the root path:

http://localhost:3000/

The dashboard displays all loaded endpoints grouped by base path, showing:

• HTTP method (GET, POST, PUT, DELETE, PATCH)
• Full endpoint path
• Response status code
• Content type

Quick Start Example

1. Export a HAR file from your browser's DevTools (Network tab → Right-click → Save all as HAR)

2. Start the proxy server:

   har-proxy my-api-recording.har -p 3000

3. Output:

   Loading HAR file: /path/to/my-api-recording.har
   
   🚀 HAR Proxy server running at http://localhost:3000
   📊 Dashboard available at http://localhost:3000/
   📦 Loaded 15 endpoints
   🌐 CORS: enabled (default)
   
   Press Ctrl+C to stop the server

4. Access your mocked endpoints:

   # If HAR contained GET /api/users
   curl http://localhost:3000/proxy/api/users

How It Works

1. Parse: Reads and parses the HAR file to extract HTTP request/response pairs
2. Map: Creates an endpoint map where later entries override earlier ones (latest wins)
3. Serve: Starts an HTTP server that matches incoming requests to recorded responses
4. Dashboard: Generates an HTML dashboard for easy endpoint discovery

Use Cases

• Frontend Development: Mock backend APIs during UI development
• Testing: Create reproducible test environments with recorded responses
• Demos: Showcase applications without live backend dependencies
• Debugging: Replay specific API scenarios for troubleshooting

License

ISC