Speedtest and your IP address

1. 01When you open the page, it asks bnkz.de which IP address your request comes from, and the name the network has for that address (reverse DNS). From the name it derives a hint about your provider, and from a database on my server the country.
2. 02When you press “Start test”, the page registers a run. Then it measures 15 times how long a tiny request takes to go there and back: The middle value is the ping, the average variation from one measurement to the next is the jitter. The very first request only sets up the connection and does not count.
3. 03Download: Four lines fetch random data at the same time until 8 seconds are up or 25 MB have arrived. The first quarter of the time, at most one second, does not count: In this ramp-up phase a connection is still getting up to speed. Meanwhile the page keeps measuring the ping, so you can see how sluggish the line becomes when it is full.
4. 04Upload: the same, with at most 10 MB. Your browser creates the data with its random generator (crypto.getRandomValues), and the server reads it and throws it away immediately.

The unit. Mbit/s means millions of bits per second, which is how providers count too. Divided by 8, that is megabytes per second: 100 Mbit/s download about 12 MB per second.

The limits. To keep my web hosting affordable, a run fetches at most 25 MB and sends at most 10 MB, and each connection can start six runs per hour. On very fast connections a run is therefore done after a second or two and is less accurate. Above about 250 Mbit/s my server can also slow things down. The result then says: at least this fast.

What is stored. For the limit, the server remembers for each run the start time, a random run number, the bytes used and a code derived from your IP address. The code is encrypted with a key that is created anew every day, and it cannot be reversed. After an hour the entry is gone. Measured values, IP address and name are not stored.

Why does another speed test show more? Many measure against a server in your provider’s network, very close to you, often without a cap. Here the measurement goes to my web hosting at a hoster in Germany, over the open internet, like any normal website. That is closer to what you experience day to day, but on fast connections it is often a bit lower.

Wi-Fi or cable? On Wi-Fi, walls, distance from the router and neighboring networks slow things down. If you want to know what arrives at your connection, measure with a cable directly at the router, and close other programs that are loading right now (updates, cloud, streaming).

My connection is slower than in my contract. What counts? As proof against your provider, in Germany only the Breitbandmessung (German) of the Federal Network Agency (Bundesnetzagentur) counts, with a cable and several measurements on different days. This test is a quick look, not proof.

What is a good ping? Under 20 ms is very good, up to 50 ms good, up to 100 ms is still fine for video calls. More important than the ping at rest is often the ping under load: If it rises sharply during a download, the line is congested (bufferbloat), and calls stutter as soon as someone downloads something.

How accurate is the provider information? It is only a hint from the name of your IP address. Many providers use other networks, 1&1 for example often that of Telekom; then it shows the network, not your contract. If it shows a data center, your connection probably runs through a VPN or a proxy.

And what does the browser estimate? Chrome, Edge and Opera provide a rough estimate through navigator.connection, rounded and capped at 10 Mbit/s so that it does not give you away. Firefox and Safari do not provide it at all. It is not measured.