API Rate Limiter

About

Simulate API rate limiting by intercepting fetch and XHR requests.

API Rate Limiter lets you create rules that intercept outgoing API calls and return configurable error responses (429 Too Many Requests, 503 Service Unavailable) so you can test how your app handles rate limiting without hitting real API limits.

How it works:

1. Click the extension icon and add a rate limit rule.
2. Set a URL pattern, request limit, and time window.
3. Browse normally — matching requests are counted and throttled when the limit is reached.
4. Throttled requests return your configured status code with a Retry-After header.

Features:

- URL pattern matching — use glob patterns to target specific API endpoints.
- Configurable responses — choose 429 or 503 status codes with custom Retry-After and error body.
- Visual counters — progress bars show how close each rule is to its limit.
- Per-rule toggles — enable or disable individual rules without deleting them.
- Request log — see which requests were throttled vs passed, with method, URL, and timestamp.
- Reset counters — clear request counts without removing rules.
- Import/export — save and share rule sets as JSON files.
- Intercepts fetch and XHR — covers both modern fetch() and legacy XMLHttpRequest calls.
- 100% local — no data leaves your browser. No accounts, no tracking, no servers.

Who is this for?

- Frontend developers testing rate limit error handling in their apps.
- API consumers verifying retry logic and backoff strategies.
- QA engineers simulating degraded API conditions.
- Anyone building resilient client-side code.

Privacy:

API Rate Limiter does not collect, transmit, or share any data. Your rules and request logs are stored locally using Chrome's built-in storage. No analytics, no telemetry, no third-party services.