How to detect internet speed in JavaScript?

Question

How can I create a JavaScript page that will detect the user’s internet speed and show it on the page? Something like “your internet speed is ??/?? Kb/s”.

Answer 1

As I outline in this other answer here on StackOverflow, you can do this by timing the download of files of various sizes (start small, ramp up if the connection seems to allow it), ensuring through cache headers and such that the file is really being read from the remote server and not being retrieved from cache. This doesn't necessarily require that you have a server of your own (the files could be coming from S3 or similar), but you will need somewhere to get the files from in order to test connection speed.

That said, point-in-time bandwidth tests are notoriously unreliable, being as they are impacted by other items being downloaded in other windows, the speed of your server, links en route, etc., etc. But you can get a rough idea using this sort of technique.