When comparing Thunar vs Polo, the Slant community recommends Thunar for most people. In the question“What are the best Linux file managers?” Thunar is ranked 9th while Polo is ranked 15th. The most important reason people chose Thunar is:
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.
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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 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 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)
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.
Pro Supports renaming files in bulk
With also predefined functions as insert (date, numbering,...), search/replace, etc ...
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 tho, cause it will also remove the shortcut from other command.
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 does the job
but just the job...
Pro Supports forward/back mouse buttons
Supports the M4 and M5 mouse buttons for forward/back, similarly to most browsers.
Pro Installs smoothly on Debian, Redhat and Arch based distributions
File managers in Linux have a nasty propensity for being closely tied to the distribution family from which they arose. Using Polo allows you to have an identical file management experience when shifting between machines from different branches of the Linux tree.
Pro Purposeful layout choices
Polo wants people to get the file manager they want, but it's not awash with granular layout options that take ages to understand. First select whether you want one, two, or four panes, and then select a format for each pane of either List, Icon, Tiled, or Media. That's it, you're done.
Pro Archive browsing and creation
Browse archive files as those they were just another folder, dragging and dropping files in and out of them at will while the backend uses the appropriate tools to manage the archive file itself. Archive creation includes a rich assortment of controls over compression formats and structure.
Pro Cloud storage support
Includes its own rclone macros for adding cloud storage access to the list of browsable locations that just works, a welcome relief in the sea of hacks which provide those features elsewhere in Linux. Currently supported: Dropbox, Google Drive, Microsoft OneDrive, Amazon Cloud Drive / Amazon S3, Openstack Swift (Rackspace Cloud Files, Memset Memstore, OVH), Hubic, Backblaze B2, Yandex Disk
Pro Launchpad PPA available
Debian-based distributions can leverage the apt package management system to keep Polo updated by adding the approved PPA to their apt sources, simplifying installation as well.
Pro Youtube-dl integration
Just paste a YouTube URL into a folder and Polo will download the best quality format of it and save it in that folder.
Pro Image file actions
Rotate, resize, optimize, convert formats, save for the web and many other handy features all right in the context menu.
Pro ISO file tools
Mount ISO files to loop devices with just two clicks, or spin them up as a QEMU KVM instance, and for portability there's also an option to write them to USB flash drives using a GUI dialog.
Pro Advanced PDF file controls
Perform Merge and Split operations on PDF files without needing another file handler all from the context menu. Rotate and Password Protection settings are also expressed there.
Pro Device management
Quickly mount and unmount devices from the sidebar, including support for locking and unlocking LUKS encrypted devices.
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 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 Requires plugins for some basic functions of modern file managers
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 No integrated search option
Con No Split View without a patch, which can be a deal breaker
This limitation can be quite annoying indeed.. thanks for the heads up!
Con No usable image view mode
Setting view to "icons" doesn't satisfy. The icons are too small to see the image.
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 Does not integrate well into Gnome
Con no double pane support
working all in all quite good out of the box,
but windows are too big, drag & drop is working, but useless on an one window file manager...
Even for novice users to weak for every days work
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 Image thumbnails sometimes wrong
There seems to be a bug where sometimes images get the wrong thumbnail, this can lead to data-loss.
Con Lengthy beta cycle
Polo has been in the beta stage of development for longer than hoped for, and while mostly stable, isn't yet ready to be promoted as a rock-solid replacement for file managers such as Dolphin and Nautilus.
Con Freemium model
Many of the best features mentioned as pros are only available after a one-time donation of USD$10 or more. Until then you just have a fast, good-looking and otherwise forgettable file manager.
Con No drag and drop
You can't drag from one view to another.
Con Load loop
Slow opening with annoying 'load loop' dialog.