: Use performance.now() for sub-millisecond precision. Fetch the Resource : Use the Fetch API to download the file. End the Timer : Record the time immediately upon completion.
Measuring actual internet speed in the browser is challenging because there is no native "speedometer" API. The standard approach involves downloading a file of a known size and measuring the elapsed time. javascript detect speed
: This returns a high-resolution timestamp in milliseconds, accurate to five-thousandths of a millisecond. javascript : Use performance