The failureReason read-only property of the BackgroundFetchRegistration interface returns a string with a value that indicates a reason for a background fetch failure.

If the value of this property changes, the progress event is fired at the associated BackgroundFetchRegistration object.

One of the following strings:

""

The background fetch has not completed, or was successful.

"aborted"

The operation was cancelled by the user, or abort() was called.

"bad-status"

A response had a not-ok status (a status outside the range 200-299).

"fetch-error"

A fetch failed for other reasons, for example CORS, or a network failure.

"quota-exceeded"

Storage quota was reached during the operation.

"download-total-exceeded"

The provided downloadTotal was exceeded. This value was set when the background fetch was registered.

Logging this property to the console prints the reason the fetch failed, or an empty string if it was successful or has not yet completed.

console.log(bgFetch.failureReason);