The XMLHttpRequest upload property returns an XMLHttpRequestUpload object that can be observed to monitor an upload's progress. It is an opaque object, but because it's also an XMLHttpRequestEventTarget, event listeners can be attached to track its process.

The following events can be triggered on an upload object and used to monitor the upload:

Event Event listener Description
loadstart onloadstart The upload has begun.
progress onprogress Periodically delivered to indicate the amount of progress made so far.
abort onabort The upload operation was aborted.
error onerror The upload failed due to an error.
load onload The upload completed successfully.
timeout ontimeout The upload timed out because a reply did not arrive within the time interval specified by the XMLHttpRequest.timeout.
loadend onloadend The upload finished. This event does not differentiate between success or failure, and is sent at the end of the upload regardless of the outcome. Prior to this event, one of load, error, abort, or timeout will already have been delivered to indicate why the upload ended.


Specification Status Comment
XMLHttpRequest Living Standard WHATWG living standard

Browser compatibility

ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
uploadChrome Full support 1Edge Full support 12Firefox Full support YesIE Full support 10Opera Full support YesSafari Full support 10WebView Android Full support YesChrome Android Full support 18Firefox Android Full support YesOpera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support 1.0


Full support
Full support

See also