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The ProgressEvent interface represents events measuring progress of an underlying process, like an HTTP request (for an XMLHttpRequest, or the loading of the underlying resource of an <img>, <audio>, <video>, <style> or <link>).


Creates a ProgressEvent event with the given parameters.


Also inherits properties from its parent Event.

ProgressEvent.lengthComputable Read only
Is 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.
ProgressEvent.loaded Read only
Is an unsigned long long representing the amount of work already performed by the underlying process. The ratio of work done can be calculated with the property and ProgressEvent.total. When downloading a resource using HTTP, this only represent the part of the content itself, not headers and other overhead.
ProgressEvent.total Read only
Is an unsigned long long representing the total amount of work that the underlying process is in the progress of performing. When downloading a resource using HTTP, this only represent the content itself, not headers and other overhead.


Also inherits methods from its parent Event.

Initializes a ProgressEvent created using the deprecated Document.createEvent("ProgressEvent") method.


The following example adds a ProgressEvent to a new XMLHTTPRequest and uses it to display the status of the request.

  var progressBar = document.getElementById("p"),
      client = new XMLHttpRequest()
  client.open("GET", "magical-unicorns")
  client.onprogress = function(pe) {
    if(pe.lengthComputable) {
      progressBar.max = pe.total
      progressBar.value = pe.loaded
  client.onloadend = function(pe) {
    progressBar.value = pe.loaded


Specification Status Comment
The definition of 'ProgressEvent' in that specification.
Unknown Initial definition.


We're converting our compatibility data into a machine-readable JSON format. This compatibility table still uses the old format, because we haven't yet converted the data it contains. Find out how you can help!

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
Basic support 1.0 3.5 (1.9.1) 10.0 (Yes) (Yes)
initProgressEvent() No support[1] No support[2] 10.0 No support[4] No support[3]
Feature Android Android Webview Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile Chrome for Android
Basic support (Yes) (Yes) 1.0 (1.9.1) 10.0 (Yes) (Yes) (Yes)
initProgressEvent() No support[3] No support No support[2] 10.0 No support[4] No support[3] No support

[1] This feature was implemented in Chrome 1.0, but removed in Chrome 17.0.

[2] This feature was implemented in Gecko 1.9.1 (Firefox 3.5 / Thunderbird 3.0 / SeaMonkey 2.0), but removed in Gecko 22 (Firefox 22 / Thunderbird 22 / SeaMonkey 2.19).

[3] This feature was removed at some point.

[4] This feature was removed in Opera 15.0.


  • The Event base interface.


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