This article applies only to an experimental version of Firefox for Android (Beta/Nightly formerly called Firefox Preview) that's no longer supported. Please download the supported version of Firefox for Android at the Google Play store
You can easily download files from various sites within Firefox Preview. A progress bar displays in the Notifications panel when the download begins, giving you the ability to pause/resume or cancel the download.
If the download fails, tap Try Again to restart it. If the download is successful, a confirmation pop-up displays where you can tap Open to open the file.