HTTP 429 Too Many Requests — Rate Limiting Guide

HTTP 429 Too Many Requests

A 429 response indicates that the client has exceeded the rate limit imposed by the server. This is a normal part of API usage and should be handled gracefully.

Understanding Rate Limits

APIs impose rate limits to:

• Protect server resources from abuse
• Ensure fair usage across all clients
• Prevent DDoS-like traffic from misbehaving clients
• Manage costs for metered services

Common Rate Limit Headers

X-RateLimit-Limit: 100        # Max requests per window
X-RateLimit-Remaining: 0      # Requests remaining
X-RateLimit-Reset: 1672531200 # Unix timestamp when window resets
Retry-After: 60               # Seconds to wait before retrying

Implementing Backoff

Exponential backoff with jitter:

async function fetchWithRetry(url, maxRetries = 5) {
  for (let i = 0; i < maxRetries; i++) {
    const response = await fetch(url);
    if (response.status !== 429) return response;

    const retryAfter = response.headers.get('Retry-After');
    const delay = retryAfter
      ? parseInt(retryAfter) * 1000
      : Math.min(1000 * Math.pow(2, i) + Math.random() * 1000, 30000);

    await new Promise(r => setTimeout(r, delay));
  }
  throw new Error('Rate limit exceeded after max retries');
}

Best Practices

1. Always check Retry-After header before retrying
2. Use exponential backoff with random jitter
3. Cache responses to reduce unnecessary requests
4. Batch requests where the API supports it
5. Use webhooks instead of polling when available
6. Implement request queues to spread load over time