Download a downloader (download manager) app like aDownloder. Long press on the Video URL in browser and select "Share" from the context menu. Then select share with aDownloader (or any other downloader app that you install). This should start downloading using the download manager app. This may not always work as some sites don't let you download videos. Give it a try. Make use of Firefox Android Addons *https://addons.mozilla.org/en-US/android/