How to benchmark Nginx with wrk
Benchmarking Nginx with wrk turns tuning changes into a repeatable baseline, so changes to workers, keepalive reuse, compression, caching, or proxy settings can be compared with measured request rate and latency instead of intuition.
The wrk client opens many concurrent HTTP connections and repeatedly requests one URL while reporting throughput, latency, transfer rate, and timeout evidence. The most useful runs target one stable final URL with fixed headers, because redirects, changing response bodies, or inconsistent request options make results difficult to compare across test windows.
Synthetic load can saturate the client host before it saturates Nginx, and even a short run can disturb shared environments. Use a separate load-generator host when possible, benchmark the final 200 OK URL with an explicit port and path, and pair the wrk output with server-side checks such as stub_status, access-log review, or application metrics so a faster result is not hiding timeouts or 4xx and 5xx responses.
Related: How to improve Nginx performance
Related: How to enable the Nginx stub_status page
Tool: HTTP Access Latency Log Analyzer
Steps to benchmark Nginx with wrk:
- Choose the exact benchmark URL and confirm that it returns 200 OK without a redirect.
$ curl -I -sS http://127.0.0.1:80/index.html HTTP/1.1 200 OK Server: nginx/1.28.3 (Ubuntu) Date: Sat, 06 Jun 2026 03:38:02 GMT Content-Type: text/html Content-Length: 14 Last-Modified: Sat, 06 Jun 2026 03:38:01 GMT Connection: keep-alive ETag: "6a239619-e" Accept-Ranges: bytes
Use the final URL that wrk will hit, including the explicit port, path, and any required Host header or authentication header. The upstream wrk usage examples also target an explicit host:port/path URL.
- Record the Nginx build or configuration under test before taking a baseline.
$ nginx -V nginx version: nginx/1.28.3 (Ubuntu) built with OpenSSL 3.5.5 27 Jan 2026 TLS SNI support enabled ##### snipped
If the test compares configuration changes, save the active config snapshot separately with sudo nginx -T and sanitize sensitive upstream names, IP addresses, or file paths before sharing it.
- Confirm that the optional stub_status endpoint is reachable before relying on it during the benchmark.
$ curl -sS http://127.0.0.1:80/nginx_status Active connections: 1 server accepts handled requests 2 2 2 Reading: 0 Writing: 1 Waiting: 0
The official Nginx documentation notes that stub_status is provided by ngx_http_stub_status_module and must be present in the build. If this endpoint is not available yet, configure it first.
- Run a short warm-up so caches, open file state, and keepalive reuse settle before the timed run.
$ wrk -t2 -c20 -d3s http://127.0.0.1:80/index.html Running 3s test @ http://127.0.0.1:80/index.html 2 threads and 20 connections Thread Stats Avg Stdev Max +/- Stdev Latency 168.80us 465.91us 11.26ms 97.37% Req/Sec 77.98k 21.33k 119.20k 70.00% 464952 requests in 3.00s, 114.40MB read Requests/sec: 154920.33 Transfer/sec: 38.12MBWarm-up numbers are disposable. The goal is to stabilize the target before the saved baseline.
- Capture the baseline benchmark with latency reporting enabled and save the result to a file.
$ wrk -t2 -c20 -d8s --timeout 5s --latency http://127.0.0.1:80/index.html | tee wrk-baseline.txt Running 8s test @ http://127.0.0.1:80/index.html 2 threads and 20 connections Thread Stats Avg Stdev Max +/- Stdev Latency 200.96us 603.99us 14.72ms 97.41% Req/Sec 71.95k 15.36k 103.96k 68.12% Latency Distribution 50% 108.00us 75% 159.00us 90% 246.00us 99% 2.33ms 1144679 requests in 8.00s, 281.64MB read Requests/sec: 143012.98 Transfer/sec: 35.19MBThe wrk command-line options documented upstream make --latency print percentile data and --timeout record stalled responses as timeouts instead of waiting indefinitely.
Do not run this kind of load test against a shared production endpoint without an approved test window, capacity headroom, and a rollback plan.
- Poll stub_status during the run or immediately after it to correlate client-side numbers with server-side connection state.
$ curl -sS http://127.0.0.1:80/nginx_status Active connections: 1 server accepts handled requests 1632 1632 1609658 Reading: 0 Writing: 1 Waiting: 0
accepts, handled, and requests show cumulative traffic, while Reading, Writing, and Waiting show the current connection mix. A sharp rise in active connections or writing sockets during a test can point to saturation or slow upstream responses.
- Change one Nginx setting at a time, reload if needed, and rerun the exact same wrk command into a new result file.
$ wrk -t2 -c20 -d8s --timeout 5s --latency http://127.0.0.1:80/index.html | tee wrk-after-change.txt
Keep the URL, headers, duration, threads, and connections identical between comparison runs so the server change is the only real variable.
Related: How to improve Nginx performance
- Check every saved result for socket errors, timeout counts, or non-success status evidence before comparing speed.
$ cat wrk-after-change.txt Running 8s test @ http://127.0.0.1:80/index.html 2 threads and 20 connections Thread Stats Avg Stdev Max +/- Stdev Latency 234.34us 578.85us 14.07ms 95.87% Req/Sec 62.60k 14.74k 99.09k 63.75% Latency Distribution 50% 120.00us 75% 189.00us 90% 344.00us 99% 2.61ms 997119 requests in 8.01s, 245.33MB read Socket errors: connect 0, read 0, write 0, timeout 20 Requests/sec: 124429.62 Transfer/sec: 30.62MBDo not treat a run as better just because Requests/sec improved. Discard or investigate runs that print Socket errors, timeout counts, Non-2xx or 3xx responses, or matching 4xx and 5xx signals in the access logs.
- Increase concurrency in small steps only after the baseline is stable and error-free.
$ wrk -t4 -c100 -d8s --timeout 5s --latency http://127.0.0.1:80/index.html | tee wrk-c100.txt
Jumping straight to very high connection counts can move the bottleneck to the client host, hit file descriptor limits, or flood shared upstream services before the result is useful.
- Compare saved results by focusing on request rate plus tail latency, not average latency alone.
$ cat wrk-baseline.txt Running 8s test @ http://127.0.0.1:80/index.html 2 threads and 20 connections Thread Stats Avg Stdev Max +/- Stdev Latency 395.07us 1.21ms 36.58ms 95.04% Req/Sec 59.04k 20.26k 107.49k 69.38% Latency Distribution 50% 126.00us 75% 207.00us 90% 513.00us 99% 6.45ms 939424 requests in 8.00s, 231.14MB read Requests/sec: 117369.39 Transfer/sec: 28.88MBA lower average latency can still hide worse tail behavior. Treat the 90// and //99 percentiles as first-class comparison data when tuning Nginx.