SEO Tool
Speed Test
Measures latency, download throughput, and upload throughput between your browser and the nearest Cloudflare edge. The original 2008-era tool was Flash-based; this one is plain HTTP with streamed payloads from a Worker, no plugins required.
Click Start to run latency, download, and upload tests in sequence.
Per-run details
| Phase | Bytes | Time (ms) | Mbps |
|---|
About
Latency is measured as the median of 10 zero-byte HTTP round trips to
/api/speedtest-down?bytes=0. Jitter is the standard
deviation of those samples.
Download throughput streams payloads of increasing size (1 MB, 5 MB,
10 MB, 25 MB) from /api/speedtest-down and reports the
peak Mbps observed. Upload sends the same sizes via POST to
/api/speedtest-up. Both endpoints set
Cache-Control: no-store so measurements aren't served
from a cache.
Speeds are measured in megabits per second (1 Mbps = 1,000,000 bits / second). Your ISP plan is sold in the same units. For megabytes/sec, divide by 8.
The Worker endpoints cap individual requests at 50 MB. That's enough
to saturate most home connections; a true gigabit fibre line will
finish a 25 MB download in ~200 ms and the figure becomes
latency-bound rather than bandwidth-bound. For more rigorous testing
on fast links use speed.cloudflare.com
or iperf3.