The onprogress EventHandler of the BackgroundFetchRegistration interface is an event handler that processes background fetch events.

The event fires when any of the following properties change:

  • uploaded
  • downloaded
  • result
  • failureReason


BackgroundFetchRegistration.onprogress = function;
BackgroundRegistration.addEventListener('progress', function);

Where function is the JavaScript function to execute.


The following example demonstrates how to log the progress of a download. The code first checks that a downloadTotal was provided when the background fetch was registered. This is then used to calculate the percentage, based on the downloaded property.

bgFetch.addEventListener('progress', () => {
  if (!bgFetch.downloadTotal) return;
  const percent = Math.round(bgFetch.downloaded / bgFetch.downloadTotal * 100);


Background Fetch
# dom-backgroundfetchregistration-onprogress

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