How Can I Estimate Internet Speed Using JavaScript?

How to Estimate Internet Speed in JavaScript

Question: How can I create a JavaScript page that estimates the user's internet speed and displays it on the page?

Answer:

It's challenging to accurately measure internet speed in the browser due to factors beyond the control of the web application. However, an approximate estimate can be obtained by:

1. Loading an Image with Known Size: Load an image with a large known file size, e.g., several megabytes.
2. Measuring Load Time: Track the time it takes for the image to finish loading (e.g., using the onload event listener).
3. Estimating Speed: Calculate the estimated internet speed by dividing the image file size by the measured load time.

Example:

The following JavaScript code demonstrates the process:

// Image address and file size (in bytes)
var imageAddr = "https://large-image-url";
var downloadSize = 7300000;

// Function to show progress messages
function ShowProgressMessage(msg) {
  // Display messages in the console and a UI element
}

// Function to initiate speed detection
function InitiateSpeedDetection() {
  ShowProgressMessage("Loading image...");
  window.setTimeout(MeasureConnectionSpeed, 1);
}

if (window.addEventListener) {
  window.addEventListener('load', InitiateSpeedDetection, false);
} else if (window.attachEvent) {
  window.attachEvent('onload', InitiateSpeedDetection);
}

// Function to measure connection speed
function MeasureConnectionSpeed() {
  var startTime, endTime;
  var download = new Image();

  // Event listeners for load and error
  download.onload = showResults;
  download.onerror = function (err, msg) {
    ShowProgressMessage("Invalid image or error downloading");
  };

  startTime = (new Date()).getTime();
  var cacheBuster = "?nnn=" + startTime;
  download.src = imageAddr + cacheBuster;

  // Function to show speed results
  function showResults() {
    endTime = (new Date()).getTime();
    var duration = (endTime - startTime) / 1000;
    var bitsLoaded = downloadSize * 8;
    var speedBps = (bitsLoaded / duration).toFixed(2);
    var speedKbps = (speedBps / 1024).toFixed(2);
    var speedMbps = (speedKbps / 1024).toFixed(2);

    ShowProgressMessage([
      "Your connection speed is:",
      speedBps + " bps",
      speedKbps + " kbps",
      speedMbps + " Mbps"
    ]);
  }
}

Note:

• The estimated speed is likely to be lower than your actual speed due to browser caching and other factors.
• This method is for demonstration purposes only and should not be used for reliable speed measurements.

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