API Rate Limiting is a traffic management strategy that controls the rate of incoming client requests to protect server infrastructure from overload and abuse.
API Rate Limiting is an essential API gateway and backend design pattern used to throttle excessive traffic, prevent Distributed Denial of Service (DDoS) attacks, ensure fair multi-tenant resource sharing, and manage third-party LLM operational costs.
Inspect rate limit response headers using the HTTP Headers Analyzer or test backoff retry handling with the API Request Builder.
| Header | Description | Example |
|---|---|---|
RateLimit-Limit |
Maximum requests allowed in quota window | 100 |
RateLimit-Remaining |
Quota remaining in current window | 14 |
RateLimit-Reset |
Seconds until quota window resets | 30 |
Retry-After |
Wait duration sent with HTTP 429 Too Many Requests |
60 |
| Algorithm | Mechanism | Pros & Cons |
|---|---|---|
| Token Bucket | Tokens added at constant rate up to bucket capacity | Allows short bursts; smooth average rate |
| Leaky Bucket | Requests processed at constant fixed outflow rate | Eliminates bursts; smooth steady throughput |
| Sliding Window Log | Timestamps recorded in sorted set per user | 100% accurate; higher memory footprint |
| Sliding Window Counter | Blends previous window count with current progress | Memory-efficient; highly accurate approximation |
Free, browser-based utilities to test, generate, and inspect API Rate Limiting Algorithms & HTTP 429 Headers payloads directly.
Analyze HTTP response headers for security, caching, and compliance issues.
Build and test HTTP API requests with headers, body, auth, and response visualization.
Parse, validate, explain, and build cron expressions with next run times and visual timeline.
