XMLHttpRequestUpload: progress event

Note: This feature is available in Web Workers, except for Service Workers.

The progress event is fired periodically when a request receives more data.


Use the event name in methods like addEventListener(), or set an event handler property.

addEventListener("progress", (event) => {});

onprogress = (event) => {};

Event type

Event properties

In addition to the properties listed below, properties from the parent interface, Event, are available.

lengthComputable Read only

A boolean flag indicating if the total work to be done, and the amount of work already done, by the underlying process is calculable. In other words, it tells if the progress is measurable or not.

loaded Read only

A 64-bit unsigned integer value indicating the amount of work already performed by the underlying process. The ratio of work done can be calculated by dividing total by the value of this property. When downloading a resource using HTTP, this only counts the body of the HTTP message, and doesn't include headers and other overhead.

total Read only

A 64-bit unsigned integer representing the total amount of work that the underlying process is in the progress of performing. When downloading a resource using HTTP, this is the Content-Length (the size of the body of the message), and doesn't include the headers and other overhead.


Using the progress event

You can use the progress event to get info about the progress of a lengthy upload. For a complete code example that uploads a file and displays a progress bar, see the main XMLHttpRequestUpload page.

// Each time a progress event is received we update the progress bar
// and the progress message
xhr.upload.addEventListener("progress", (event) => {
  progressBar.value = event.loaded; // Update the progress bar
  log.textContent = `Uploading (${((event.loaded / event.total) * 100).toFixed(


XMLHttpRequest Standard
# event-xhr-progress
XMLHttpRequest Standard
# handler-xhr-onprogress

Browser compatibility

BCD tables only load in the browser

See also