How to rate limit FastAPI in 2026

Rate limiting is a crucial defense against abuse in web applications. This guide explains how to implement rate limiting in a FastAPI app in 2026, step by step. Begin by installing the drogue[fastapi] package with pip install drogue[fastapi].

First, create a FastAPI application instance and initialize the DrogueLimiter object with default limits. The default limit is set to 100 requests per minute. Once the limiter is created, apply it to specific routes using the @limiter.limit decorator. For example, the /api/public route is limited to 100 requests per minute, while the /api/login route is restricted to 5 requests per minute, providing strict protection against brute force attempts.

Using the FIXED_WINDOW algorithm can help enforce a hard cap per time window without allowing short bursts. Conversely, the SLIDING_WINDOW algorithm provides smooth rate limiting with no boundary spikes, making it ideal for fair API usage. GCRA and LEAKY_BUCKET algorithms offer additional options for high-throughput APIs and background jobs, respectively.

For custom identity and per-route limits, use the HeaderExtractor class from drogue.core.identity. Custom identity allows you to use attributes other than IP addresses for rate limiting. RedisStorage is useful when you need to enable rate limits across multiple processes and workers. With RedisStorage, rate limits are shared across all workers and processes.

In case you want to override default error responses, create a custom error renderer function that returns a 429 response with JSON data. Finally, for WebSocket rate limiting, use the @limiter.limit_ws decorator, specifying the desired limit in requests per minute.