MockFill: API Mocking

Mock and intercept fetch/XHR APIs in your browser with rule-based responses, delays, headers, presets, and quick toggles.

MockFill: API Mocking is a developer-focused Chrome extension for mocking HTTP APIs directly in the browser.

Test frontend flows without touching backend code:
- Simulate success, empty, and error responses
- Test loading states with response delays
- Validate UI behavior for edge cases
- Work faster on localhost, staging, or any web app

What you can do:
- Intercept both `fetch` and `XMLHttpRequest` calls
- Match requests by URL pattern (string or regex) and HTTP method
- Configure custom response status, body, headers, and delay
- Enable/disable mocking globally or per rule
- Reorder rules to control matching priority
- Track hit counts for each mock rule
- Import/export mock rules as JSON
- Import from cURL to create rules quickly
- Save presets for different testing scenarios and switch instantly

Built for:
- Frontend developers
- QA engineers
- Teams testing API-dependent UI states

Why MockFill: API Mocking
- No backend changes required
- No external proxy setup
- Fast, repeatable API testing workflow inside Chrome

Privacy:
- Rules and settings are stored locally in your browser.
- No API payloads are sent to external servers by the extension.