Why do speed tests give different results?
A speed test measures the path to one test server, using one method, on one device, at one moment, so two tests rarely agree. A gap of 10 to 20% between runs or between tools is common. For a fair comparison, use the same device on a cable, the same test, and the middle result of three runs.
Why results differ
- Different servers. Some tests use servers hosted by internet providers, and others use servers on a content network. A test to a nearby server inside your provider's network often reads higher than one that crosses to a different network. SpeedUp tests to the nearest Cloudflare server.
- Different methods. Tests differ in how many connections they run in parallel, how long they last, whether they skip a warm-up period and how they average the result. Connections also start slowly, so a very short test can read low.
- Wi-Fi changes second to second. Distance, walls and other networks change your signal between two runs.
- Your device and browser. An older phone, a busy processor or heavy browser extensions can limit what the test can measure on a fast connection.
- Background traffic. Updates, backups and other people's streams share the line during the test.
- Time of day. Evenings can be slower on shared networks.
- VPNs and relays. A VPN, a proxy or iCloud Private Relay changes the route, and speed tests then measure that route.
- Units. One tool may show Mbps and another MB/s. See Mbps vs MB/s.
Which test should you trust?
No single test is perfect. They measure different paths, and none is simply wrong. What matters is consistency. Pick one test, run it under the same conditions, and watch how it changes over time. If two different tests on a cable agree within about 20%, you can treat the result as reliable.
How to compare tests fairly
- Use the same device for every test, connected by cable if you can.
- Close other apps and pause updates and backups.
- Turn off any VPN, proxy or iCloud Private Relay.
- Run each tool two or three times back to back, and take the middle result.
- Repeat at different times of day.
What the SpeedUp test does
SpeedUp measures your connection to the nearest Cloudflare server. It sends small requests to get your ping and jitter, runs several parallel download streams for 10 seconds after ignoring the first 2 seconds of ramp-up, keeps pinging during the download to measure bufferbloat, and then tests upload for 7 seconds. Because it tests to Cloudflare, its numbers can differ from a test that uses your provider's own servers. They are different paths, and neither is wrong.