How to Detect Network Speed using JavaScript? Last Updated : 21 Apr, 2025 Summarize Comments Improve Suggest changes Share Like Article Like Report Network speed detection in JavaScript involves measuring the time it takes to download a known file or resource and calculating the download speed. To calculate the speed of the network a file of known size is chosen from a server to download. The time taken to start and complete the download is recorded and using the file size and the time taken, the download speed is calculated.ApproachOpen the web page for which you want to know the connection speed. The page should be the one for which you want to add the JavaScript code for detecting the speed. Assign or set up the address of the image that you want to use for the speed test to the variable. The variables for storing the test's start time, end time, and download size should be created. Set the "download Size" equivalent to the image file size(In bytes). The end of the download action is assigned to activate when the image downloading is completed. It calculates the speed of the download process, and converts it to "kbps" and "mbps". Example: Below is an example illustrating the above approach. HTML <!DOCTYPE html> <html> <head> <title> To detect network speed using JavaScript </title> </head> <body> <script type="text/javascript"> let userImageLink = "https://media.geeksforgeeks.org/wp-content/cdn-uploads/20200714180638/CIP_Launch-banner.png"; let time_start, end_time; // The size in bytes let downloadSize = 5616998; let downloadImgSrc = new Image(); downloadImgSrc.onload = function () { end_time = new Date().getTime(); displaySpeed(); }; time_start = new Date().getTime(); downloadImgSrc.src = userImageLink; function displaySpeed() { let timeDuration = (end_time - time_start) / 1000; let loadedBits = downloadSize * 8; /* Converts a number into string using toFixed(2) rounding to 2 */ let bps = (loadedBits / timeDuration).toFixed(2); let speedInKbps = (bps / 1024).toFixed(2); let speedInMbps = (speedInKbps / 1024).toFixed(2); alert("Your internet connection speed is: \n" + bps + " bps\n" + speedInKbps + " kbps\n" + speedInMbps + " Mbps\n"); } </script> </body> </html> Output: Comment More infoAdvertise with us Next Article How to Detect Network Speed using JavaScript? 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