What is Download Manager (S3)? Despite its compact size, Download Manager (S3) packs in a bunch of useful features that standard download utilities don’t provide. Its fully customizable interface automatically disappears when not in use - giving you full control without interruption. Features:

Displays download progress, time remaining, full file path, URL, etc.
Hides status bar when all downloads are complete
Position buttons in the download bar where you prefer
Ability to show only the number of completed downloads
Preview image files
Can pause, cancel, resume, or re-try single and group downloads
Replace Downloads Library page - you have full control of your download history
Change the text and tooltip sizes
Has a Queue mode
Shows «Download complete» notification

Hotkeys (by default for Windows):

Ctrl + J = open Download History page
Ctrl + Shift + Z = show/hide Download Bar
Ctrl + Shift + Backspace = clear the last downloaded item
Ctrl + Shift + Insert = undo last clear
Ctrl + Shift + Enter = open the last downloaded item
Alt + Shift + Enter = show the last downloaded item

WebExtensions Limitations:

Download Bar not displayed on some sites from mozilla.org and google.com
Download Bar not displayed on sites that do not have pages, for example error 404 (page not found)
Download Bar not displayed on internal Firefox and GoogleChrome pages, for example about:addons , about:config , chrome://extensions/ , chrome://settings/ , etc.
Download Bar not displayed on the extensions pages "moz-extension://...." , "chrome-extension://...."

============ You also can use Download Manager (S3) for Google Chrome: https://chrome.google.com/webstore/detail/download-manager-s3/ngmcjenopiialholjggicgplegmcmjda ============ Download Manager (S3) is full compatibility for Google Chrome, but there are known problems for Firefox:

downloadItem.exists does not change from true to false when a file is removed https://bugzilla.mozilla.org/show_bug.cgi?id=1381031
does not display history from past sessions https://bugzilla.mozilla.org/show_bug.cgi?id=1255507
chrome.downloads.drag is not a function https://bugzilla.mozilla.org/show_bug.cgi?id=1245648

--- forums mozillaZine: http://forums.mozillazine.org/viewtopic.php?t=2793995 forums mozilla-russia: https://forum.mozilla-russia.org/viewtopic.php?id=73317