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API Rate Limiter Calculator

Design and visualize rate limiting strategies. Compare token bucket, sliding window, and fixed window algorithms. Generate implementation code. Ctrl+Enter to calculate, Ctrl+Shift+C to copy results.

Presets

Configuration

Results

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Requests / Second
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Requests / Minute
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Requests / Hour
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Max Burst Capacity
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Refill Rate (tok/sec)
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Burst Recovery Time
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Daily Quota
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Monthly Quota
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Avg Wait if Throttled

Traffic Simulation

Allowed Denied Available Tokens

Implementation Code


            

        


        

            
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Frequently Asked Questions

        

            What is API rate limiting?▼
            
API rate limiting is a technique used to control how many requests a client can make to an API within a given time window. It protects servers from being overwhelmed, ensures fair usage among clients, and prevents abuse. Common implementations return HTTP 429 (Too Many Requests) when a client exceeds the allowed rate, along with headers like X-RateLimit-Remaining and Retry-After to help clients manage their request pacing.

        

        

            What is the difference between token bucket and sliding window?▼
            
The token bucket algorithm allows bursts of traffic up to the bucket capacity while maintaining an average rate by refilling tokens at a steady pace. This is ideal for APIs that need to handle occasional traffic spikes. The sliding window algorithm tracks requests within a continuously moving time window, providing smoother rate limiting without allowing large bursts. Fixed window is the simplest approach but can allow up to 2x the rate at window boundaries. Token bucket is used by AWS and Stripe, while sliding window is popular for APIs requiring strict, predictable limits.

        

        

            How do I choose the right rate limit for my API?▼
            
Consider these factors: 1) Server capacity -- measure how many requests per second your backend can handle and set limits well below that threshold. 2) User experience -- limits that are too low frustrate developers. Start generous and tighten as needed. 3) Endpoint cost -- expensive operations like search or file uploads should have lower limits than simple reads. 4) Client tiers -- offer higher limits for authenticated or premium users. 5) Industry norms -- GitHub allows 5,000/hour for authenticated requests, Twitter allows 300/15 minutes, and Stripe allows 100/second.