Takes about 20 seconds
Settings
Server: the nearest Cloudflare data centre, chosen automatically. Load: speed.cloudflare.com.
Ping
The time a small request takes to reach the test server and come back. Lower is better.
Jitter
How much that time wobbles from one request to the next. Steady is better.
Lost requests
Requests that failed or took over 2 seconds. Zero is the goal.
Bufferbloat
How much the delay rises while your line is busy. The grade is based on this.
What a bufferbloat test checks
Bufferbloat is extra delay caused when routers and modems hold too much data in a queue while the line is full. Bufferbloat.net describes it as high latency (lag) that shows up when there is other traffic on your network. A good test therefore compares two things: your latency when the line is quiet, and your latency while it is busy uploading or downloading. Latency simply means the time it takes a small piece of data to reach a server and come back.
Your connection can feel fast on a speed test and still stutter on a video call the moment someone starts a download. That gap is what this page is for. A bufferbloat test looks at how responsive your connection stays when it is working hard, not just how many megabits it can move.
How to read your result
The number that matters most is the increase: how many milliseconds your latency rises under load. Bufferbloat.net's guidance is that if latency stays below roughly 15–25 ms during the test, bufferbloat is under control. If it climbs much higher, you likely have bufferbloat, and calls, games and browsing will feel sluggish whenever the line is busy.
| Grade | Extra latency under load (worst of download and upload) |
|---|---|
| A+ | 5 ms or less |
| A | more than 5, up to 30 ms |
| B | more than 30, up to 60 ms |
| C | more than 60, up to 200 ms |
| D | more than 200, up to 400 ms |
| F | more than 400 ms, or no answer under load |
The grade is based only on how much latency rises under load. Ping, jitter and lost requests get their own Good, OK or High label.
Getting a fair reading
- Use a wired connection if you can, so Wi‑Fi problems don't hide the router queue.
- Pause big downloads, cloud backups and streams on other devices first.
- Run the test two or three times, at different times of day.
What to do next
If your latency jumps under load, the usual fix is Smart Queue Management (SQM) on your router. Our guide How to fix bufferbloat walks through it step by step. Want the background first? Read What is bufferbloat?. You can also check single measurements with the ping test, jitter test, packet loss test and latency test.
Lag when the line is busy?
Our step-by-step guide shows how to turn on Smart Queue Management and test again.
How we measure
How this test measures. A browser cannot send a classic ICMP ping, so this test times small web requests (HTTP round trips) from your browser to the nearest Cloudflare data centre that serves this site, one request every 0.2 seconds. Each round trip includes a little browser and server processing, so it can read a few milliseconds higher than a classic ping.
In this order: about 5 seconds on a quiet line (the first 2 requests are a warm-up and not counted, so a standard test keeps about 20–25 idle round trips), then 8 seconds while your browser downloads test data from speed.cloudflare.com over 4 connections, then 8 seconds while it uploads test data to speed.cloudflare.com over 4 connections. The round trips keep running during both loads; how many fit in depends on how slow they get. The “Long” setting uses 8, 15 and 15 seconds.
The numbers: ping is the median of the idle round trips (the result also shows the fastest and slowest). Jitter is the average difference between one idle round trip and the next. Bufferbloat is the median round trip during download minus the idle median, and the same for upload; the grade uses the larger of the two. Lost requests counts round trips that failed or took longer than 2 seconds, out of all that were sent. Download and upload speed during the test are shown too.
Nothing is stored. Your result stays on your screen. It is not saved and not sent to us, and there is no account. Nothing to install: it all runs in your browser.
FAQ
Is this the same as a speed test?
No. A speed test mainly reports how much data per second you can move. A bufferbloat test focuses on delay while the line is full, which is what you notice as lag.
Will a faster internet plan fix bufferbloat?
Not necessarily. Bufferbloat.net points out that the problem is excess buffering in the router or modem, and extra speed does not remove that delay.
Why is my result different each time?
Other traffic on your network and your provider's network changes from minute to minute. Running the test a few times gives a more honest picture.
Do I need to install anything?
Yes. It runs in your browser with nothing to install.