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

Event listerers that can be trigerred on an upload object are the following:

Event listeners Data type of response property
onloadstart The fetch starts
onprogress Data transfer is going on
onabort The fetch operation was aborted
onerror The fetch failed
onload The fetch succeeded
ontimeout The fetch operation didn't complete by the timeout the author specified
onloadend The fetch operation completed (either success or failure)


Specification Status Comment
XMLHttpRequest Living Standard WHATWG living standard

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support ? ? ? ? ?
Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support ? ? ? ? ? ?


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AJAX API Property Read-only Reference XMLHttpRequest