API Response Time Tester
Measure endpoint latency with multiple pings. See min, max, average, and percentile stats.
Configuration
Note: browsers restrict cross-origin requests due to CORS. The target server must send Access-Control-Allow-Origin headers for this tool to work.
Monitor endpoint performance over time
Recuro tracks response times, success rates, and alerts you when things slow down.
Why API response time matters
Response time is the most fundamental metric for any API. It directly affects user experience, conversion rates, and system reliability. Studies consistently show that every 100ms of added latency reduces conversion by measurable percentages. For APIs that power real-time features — search autocomplete, payment processing, webhook deliveries — every millisecond counts.
Averages can be misleading. An API with a 50ms average might have a p99 of 2 seconds, meaning 1 in 100 users waits 40 times longer than typical. This is called tail latency, and it is often caused by garbage collection pauses, database connection pool exhaustion, cold starts in serverless functions, or cache misses. Percentile metrics (p50, p95, p99) give you a much clearer picture of real-world performance.
A single test gives you a snapshot, but performance varies throughout the day. Traffic spikes, deployment rollouts, and infrastructure changes all affect response times. That is why continuous monitoring matters more than one-off tests.
With Recuro, you can schedule HTTP health checks on any cron expression — every minute, every 5 minutes, or any custom schedule. Recuro records response times, tracks success rates, retries failed requests, and sends alerts when performance degrades. Turn this one-time test into ongoing visibility.
Frequently Asked Questions
What is p99 latency and why does it matter?
P99 latency is the response time at the 99th percentile — meaning 99% of requests complete faster than this value. It captures the worst-case experience for your users. A low average latency can hide occasional slow requests that frustrate real users. Monitoring p99 (and p95) helps you detect tail latency issues that averages alone would mask, such as garbage collection pauses, cold starts, or database lock contention.
How accurate are browser-based response time measurements?
Browser-based measurements include network round-trip time, DNS resolution, TLS handshake, and server processing time — which is exactly what your users experience. However, they are subject to CORS restrictions: if the target server does not send Access-Control-Allow-Origin headers, the browser will block the response entirely. For endpoints you control, this tool gives a realistic picture of end-to-end latency. For third-party APIs, you may need a server-side monitoring tool.
How many pings should I send to get reliable results?
For a quick check, 5 pings is usually enough to spot obvious issues. For more statistically meaningful results, use 10-20 pings. The first request is often slower due to DNS resolution and TLS handshake (cold start), so comparing the first ping to subsequent ones can reveal connection overhead. Consistent results across all pings indicate a stable endpoint; high variance suggests intermittent issues.
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