True Speed & Lag Test
Most speed tests stop at "how fast". This one also fills your line step by step and measures how much lag builds up as it gets busy, which is what makes video calls freeze and games stutter when someone else is streaming or uploading.
- Real sustained speed
- Lag under load
- Call quality score
Your connection
- IP address
- 216.73.216.145
- Provider
- Amazon.com, Inc. AS16509
- Test server
- osir.co.uk, United Kingdom
For a true result, use a wired connection if you can, pause downloads, streaming and backups on other devices, and close other tabs.
Run the test
Takes about 2 minutes.
Advanced settings
Repeating the test shows how your line changes through the day, for example at busy evening times. Keep this tab open while a series runs.
Live
- 1 Top speed
- 2 Download under load
- 3 Upload under load
- 4 Call quality
Press Start the test when you're ready.
Download
- Top speed
- -
- Lag-free speed
- -
- Worst lag
- -
- Probes lost
- -
Upload
- Top speed
- -
- Lag-free speed
- -
- Worst lag
- -
- Probes lost
- -
Lag as your line fills up
We loaded your line at each level for a few seconds and timed small probes the whole time. On a well-managed line the lines stay flat; a line that climbs as the load rises has bufferbloat.
Download steps
| Load | Speed | Ping | Jitter | Lost | Result |
|---|
Upload steps
| Load | Speed | Ping | Jitter | Lost | Result |
|---|
Call quality
Scored from 1 (unusable) to 4.5 (perfect) using the ITU-T E-model, the industry standard for predicting voice quality. The big number is quality while your line is moderately busy; "idle" is the best case.
Call quality as the line fills
Each row uses the worse of downloading and uploading at that load, counting only loads we actually reached.
Your runs
Every run in this tab, newest last.
| # | Time | Download | Upload | Idle ping | Lag grade | Worst lag | Calls under load | Notes |
|---|
Technical log
What this test does
- Top speed: downloads and uploads as fast as your line allows for about 10 seconds each, ignoring the slow first moments.
- Download and upload under load: runs your line at 100%, 80%, 60% and so on of that speed, timing small probes all the while. That shows how much lag builds up at each level.
- Call quality: turns the lag, jitter and lost probes into a call quality score for four common voice codecs, both idle and under load.
Lag grades
- A+ / A: under 25 ms of extra lag at full load. Calls and games stay smooth while the line is busy.
- B: 25 to 50 ms. Mostly fine; competitive gaming may notice.
- C / D: 50 to 200 ms. Calls get choppy when someone else downloads or uploads.
- F: over 200 ms. Calls and games fall apart whenever the line is busy.
What is bufferbloat?
When a line is full, your router and your provider's equipment queue up the extra data instead of dropping it. Big queues keep downloads fast but make everything else wait in line, so a video call or game can suffer a second or more of lag while someone else is streaming or uploading. This test measures it by timing small probes while it fills your line.
How do I fix a poor lag grade?
Look for "Smart Queue Management" (SQM), "QoS" or "bandwidth control" in your router settings, often using the CAKE or fq_codel method, and set it to about 90% of the speeds shown here. Many modern routers, mesh systems and business firewalls support it. Your provider can also tell you whether their equipment manages queues.
Why is my speed lower than my package?
Wi-Fi, other devices on your network, the time of day and the distance to our UK server all count. A wired test with everything else paused is the fairest. If wired results are regularly far below what you pay for, show your provider a few results from different times of day.
Why measure "lost probes" rather than packet loss?
A web page can't send raw network packets. Lost data is resent automatically, so instead it shows up as a probe that takes more than three seconds, which is what we count. Small amounts of real packet loss appear as jitter and lag spikes.
Does the test use much data?
A standard test transfers about 25 seconds' worth of your line's full speed in each direction. On a 100 Mbps line that's roughly 300 MB of downloading. Avoid running it on a capped mobile plan.
Why might I have to wait in a queue?
Two tests at once would share our server's connection and each would measure the other. So tests take turns, and the page starts yours automatically when it's free.