Thunar is a modern file manager for the Xfce Desktop Environment.
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Pro Minimal dependencies
Unlike Nautilus, which requires the whole GNOME desktop, thunar just depends on some XFCE utilities & GTK.
Pro Supports "quick-directory" typing
While in a Thunar window, typing either a "~" or a "/" will automatically start typing into the "address-bar" and pressing enter goes straight to the typed directory.
Pro Custom actions are easy to set up
Use Custom Actions to add right-click options to do things like Open as Root, Open Git GUI, etc. You can filter the file types and filename patterns that the actions will show up for.
To add an "Open as Root" action, go to Edit, Configure custom actions. Assign a name and a description. Set Command as "gksudo xdg-open %f" (you'll need to install gksudo since pkexec won't work). Pick an icon (I prefer "changes-allow"). Under Appearance Conditions, select Directories, Text Files, and Other Files.
Pro Non-recursive find
In a thunar window, any non-directory typing will search in the current directory for the filename that you type (non-recursive, unlike Nautilus)
Pro Supports renaming files in bulk
With also predefined functions as insert (date, numbering,...), search/replace, etc ...
Pro Supports forward/back mouse buttons
Supports the M4 and M5 mouse buttons for forward/back, similarly to most browsers.
Pro Does the job
But nothing more.
Pro Keypress to search in folder
While in a Thunar window, typing a filename automatically selects the first matching file in the current folder.
Pro Can assign custom shortcuts to scripts in XFCE
Thunar can use the editable accelerator feature of XFCE.
xfce4-appearance-settings in terminal, go to settings tab, check "enable editable accelerator". Now open any command in Thunar menu, hover to a command, i.e. your custom "places" or your custom command, then press any combination to assign a shortcut to it.
be careful though, cause it will also remove the shortcut from other command.
Use tabs to open fewer windows. New tabs automatically start in the same location. Tabs can be detached.
Pro Select by Pattern
Select multiple files in the current folder using a wildcard pattern.
Con No integrated search option
Con No usable image view mode
Setting view to "icons" doesn't satisfy. The icons are too small to see the image.
Con Simplified action bar
The action bar on Thunar is very simple and doesn't have as many features and buttons as other file managers. It only has a back, forward, up, and home buttons as well as the folder path.
Con Does not integrate well into Gnome
Con Tree sidepane missing features
When the sidepane is in Tree mode, it does not show Places (Favorites). It also doesn't collapse folders (like Windows Explorer), adding to clutter.
Con Requires GNOME dependencies to support common features
Thunar relies on GVFS to support mounting disks or accessing web folders, however since GVFS is a third party GNOME library and made for the use in the GNOME environment its often incompatible to Thunar stable releases which results into crashes and other issues
Con No double pane support
Working all in all quite good out of the box, but the windows are too big. Drag & drop is working, but useless on a one-window file manager. Even for novice users it's too weak for everyday work.
Con Requires plugins for some basic functions of modern file managers
Con No Split View without a patch
Which can be a deal breaker.
Con Moving files
Has serious problems moving files. It may stop abruptly with some undefined error message and the files would be gone afterwards.
Con Won't write to any removable media that has been on an Apple machine
Removing dot-files that Apple puts on the media (like .fseversd) allows Thunar to write to it.
Con Doesn't integrate well with archive manager other than Xarchiver
"Extract here" function doesn't integrate well with archive manager other than Xarchiver (e.g. Ark, GNOME Archive Manager).
Con Image thumbnails sometimes wrong
There seems to be a bug where sometimes images get the wrong thumbnail, this can lead to data-loss.
Con Slightly unstable
Thunar crashes some times on file moves, copy-pasting etc. The developers are working on it, but it's taken a while.
Con No progress bar when copying/moving file
Either this is problem with XFCE4 or Thunar, but there's no progress bar when copying/moving file with Thunar.
The only way to tell whether it finished is CPU usage.