What is Rate Limiting?
Rate limiting is a technique that controls the number of requests a client can make to a server within a specified time window. It protects servers from abuse, prevents DDoS attacks, ensures fair resource usage, and maintains service availability for all users.
How Does Rate Limiting Work?
Rate limiting works by tracking the number of requests from each client (typically identified by IP address, API key, or user account) and rejecting requests that exceed the configured threshold. Common algorithms include fixed window (counting requests in set time periods), sliding window (using a moving time frame), token bucket (allowing burst traffic up to a limit), and leaky bucket (processing requests at a steady rate). When a limit is exceeded, the server returns a 429 Too Many Requests status code.
In web hosting and API management, rate limiting is essential for protecting backend services from overload and abuse. It prevents brute-force login attacks, API scraping, and denial-of-service attempts. Rate limits are typically communicated through HTTP headers like X-RateLimit-Limit, X-RateLimit-Remaining, and X-RateLimit-Reset. Web servers like Nginx include built-in rate limiting modules, CDNs like Cloudflare offer configurable rate limiting rules, and API gateways provide sophisticated rate limiting per endpoint, user tier, or API key.