The XMLHttpRequest upload property returns an XMLHttpRequestUpload object that can be observed to monitor the progress of an upload. It is an opaque object, but being an XMLHttpRequestEventTarget, event listeners can be set on it to track its process.

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

Event Event listener Description
loadstart onloadstart The upload has begun.
progress onprogress Periodically delivered to indicate the current 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 an awaited reply did not arrive within the time interval specified by the timeout property on the XMLHttpRequest.
loadend onloadend The upload completed; this event does not differentiate between success or failure, and is sent at the very end of the upload process, regardless of the outcome. Prior to this event being sent, one of load, error, abort, or timeout will already have been delivered to indicate why the upload is ending.

Specifications

Specification Status Comment
XMLHttpRequest Living Standard WHATWG living standard

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support112 Yes ? Yes10
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support Yes1 ? ? Yes ? Yes

See also