Are you trying to use '''Firefox Send'''? https://support.mozilla.org/en-US/kb/send-files-anyone-securely-firefox-send The "arrow" which appears intermittently is for '''Downloads''' and is for accessing downloaded files within the current session. Hidden before a download is done and hidden again in subsequent sessions. Although there is a way to have it appear all the time on the Navigation Toolbar. But that isn't for uploads.