API Pilot - API Interceptor, Mocker & Tester

Intercept. Mock. Test. Master your API flows.

API Pilot is the ultimate browser extension for frontend developers, QA engineers, and API designers. It empowers you to take full control of your browser's network traffic, interview APIs, and simulate any server scenario without writing a single line of backend code.

Key Features

🚀 Advanced Request Interception

Take full control of your browser's network layer. Monitor and modify XMLHttpRequest (XHR) and Fetch API calls in real-time.

• Granular Matching: Targeting requests using Wildcards (*), Exact Match, or powerful Regex patterns (^/api/v1/users/\d+$).
• Method Filtering: Filter by specific HTTP methods (GET, POST, PUT, DELETE, PATCH, OPTIONS).
• Resource Types: Control traffic for XHR, Fetch, Scripts, Stylesheets, Images, and more.
• Rule Management: Organize rules with custom names, toggle individual rules with a single click (Play/Pause), and manage rule sets with easy Import/Export (JSON) capabilities.

🧪 API Tester (Built-in REST Client)

No need to switch between your browser and external tools like Postman. Test APIs directly within your browser context.

• Full Request Builder: Support for all standard HTTP methods.
• Param & Header Management: Key-value visual editors for query parameters and headers.
• Body Support: Editors for JSON, Raw Text, and URL-Encoded bodies.
• Auth Support: Built-in support for Bearer Token and Basic Auth.
• History & Saved Requests: Auto-saves request history and allows you to "bookmark" favorite API calls for quick access.
• cURL Import: Paste any cURL command to instantly populate the tester.

🎭 Powerful Mocking Capabilities

Eliminate dependencies on unstable or unfinished backend APIs.

• Static Mocking: Return fixed JSON, XML, or Text responses instantly.
• Dynamic Mocking: Use JavaScript rules to conditionally modify real API responses (e.g., if request param id=5 then return role: "admin").
• Status Code Simulation: Test how your app handles 404s, 500s, 403s, or any other status code.
• Response Modification: Modify existing response headers or bodies on the fly.

🌍 Environment Management

Manage variables for different environments (Local, Staging, Production) and switch between them instantly.

• Variable Substitution: Use {{baseUrl}} or {{apiKey}} in your rules and requests.
• Context Switching: Change your entire testing context with one click.

⚡ Network Simulation

Test your application's resilience under various network conditions.

• Latency Injection: Add artificial delays (ms) to specific endpoints to simulate slow connections or race conditions.
• Error Injection: Force specific requests to fail to verify error handling UI.

🛠 Header & Request Modification

• Inject Headers: Add custom authentication tokens or debug flags (X-Test-Mode: true) to outgoing requests.
• Modify Response Headers: Test CORS scenarios by overriding Access-Control-Allow-Origin.
• Redirects: seamlessly redirect API calls from production (api.prod.com) to localhost (localhost:3000) or a staging environment.

Use Cases

For Frontend Developers

• Develop Locally: Build frontend features even when the backend API is down or not yet implemented.
• Edge Case Testing: Instantly reproduce bugs by mocking specific server states (e.g., empty lists, extremely large datasets, server errors).

For QA Engineers

• Isolate Visual Bugs: Verify if a bug is frontend or backend related by controlling the data returned to the UI.
• Automation: Export and share rule sets with your team to ensure consistent testing environments.

For API Designers

• Prototyping: Mock the proposed API structure and get feedback from frontend teams before writing the actual implementation.

Security & Privacy

• Local First: All rules and mocks are stored locally in your browser. No data is sent to external servers.
• Open Source Core: Built on transparent and secure browser extension APIs (declarativeNetRequest).

Supported Platforms

• Google Chrome
• Mozilla Firefox
• Microsoft Edge
• Brave Browser
• Opera

Ready to take control of your network? Download today.