■ Slow to start or/and slow to run, what's wrong?

"Smaller, faster, more efficient", that's what xplorer² was designed to be, and for most people that's the way things are. The other day some customer wrote complaining about slow starts; it turned out that the gentleman had 20-odd tabs showining and sorting by Signed by (authenticode) column. xplorer² was designed to be best of class but it cannot bend the laws of physics. When you ask too much of the program and use many of the advanced features simultaneously, and when your folders have too many items in them, then inevitably things will slow down.

Sometimes the cause of delays is evident (e.g. that rusty 386 of yours with windows 8 installed :) but would you have imagined that having too many icons in your custom commands would be a factor? Below I enumerate a few common issues with workarounds that will help you speed up your file management experience.

1. Slow starts troubleshooter

Too many tabs?. When xplorer² starts it will try to read all tabs from the last session. Are you sure you need to browse all these folders simultaneously? You can use /T command line switch to avoid loading previous tabs.
Unavailable network locations? If you leave xplorer² browsing some network place that is not connected when you restart it, you will see a long delay. Use the /N command line switch to avoid loading slow network folders, or specify the starting folders from the command line to something fast and available like C:\ drive as such: xplorer2_64.exe /T /1 C:\
Network items in the miniscrap? If you use the miniscrap pane and store remote items in there, you run the same risk as if browsing an unavailable network folder. Instead of storing the direct item use a local shortcut to it.
Too many color tags? xplorer² stores color tags in the database file shell:appdata\zabkat\tagdb.bin. If this file gets too big, it will somehow slow down the start. If you don't use color tags consider deleting this file (while xplorer² isn't running).
Portable settings. If you install ultimate edition permanently on your hard disc, save settings in registry, not some INI file. Loading/saving settings from INI files is much slower and only meant for portable use off a USB stick.
Too many user commands with custom icons? This was a suprise find during profiling. If you have too many user commands (or any other list under Customize menu with custom icons), loading all these icons will make xplorer² start slower. Consider switching some commands to their Plain icons that load faster (using the Organize menu command for e.g. user commands).

Another obvious workaround is to start xplorer² and leave it running. Then whatever factors cause slow starts will only be suffered once. Whenever you need to browse folders just grab xplorer² from the taskbar. When you have xplorer² set to replace windows explorer, the program stays in memory even when you close the window — just avoid using File > Exit or <Alt+X> command (that will fully quit xplorer²).

2. Generally slow to run

Too many details? The more columns you show in detailed view mode, the harder xplorer² must work to fill them up. Some columns are slower than others, but in general background threading will handle them nicely. Just make sure you don't disable threading (check your Tools > Advanced options menu that Background priority is set to Normal).
xplorer² extracts some slow information in a background thread, including file icons. However you don't need to wait till all icons appear, you can start using your folder immediately while xplorer² is lazily extracting icons and other slow details.
Sort by slow column? If you sort by the Checksum or other slow columns, things are going to get really slow and threading won't help. At least set the default mode to be sorting by Name or Date (see View > Arrange by menu or just click on the Name column header).
Other advanced modes. xplorer² has many features that rely on complex filters, e.g. you can have all files with the Encrypted attribute showing with blue color. Such rules rely on file attributes and as we've seen some attributes are slower than others. If you use too many color coding or custom grouping rules, things will slow down, especially in folders with lots of files in them.
Automatic folder sizes. If you tick the option to "Calculate folder sizes automatically", xplorer² will consume many resources, especially when browsing top level folders like C:\ . xplorer² will remain responsive but things will feel altogether sluggish. Do you really need to know the subfolder size every time you browse some folder? Use Tools > Folder statistics command only when you really need to see what's stored in a folder hierarchy.
Network folders. Everything is slower when you access a remote folder. Ticking the advanced option "Faster network access with plain icons" will help speed things up. You get a somewhat poorer experience (plain icons, no overlays, no infotips, no folder sizes) but the sacrifice is worth the prize!
Slow copying?. If you are copying huge files (>1 GB) then xplorer² robust copy gets into a safe (and slower) unbuffered mode, to protect your system memory from getting clogged up. You can turn this feature off using Tools > Advanced options menu command (set "Huge file limit" to 0).
Or have you perhaps enabled copy speed throttling? You can turn it off through advanced options too
Slow file search?. Unless you want to search inside archives (zipfolders, 7z folders and the like), make sure Archived content box in the find files dialog is not ticked. If you are searching for text within files, it will take much longer; if your target files are plain text, don't tick "search all files" — but that won't work for what most people consider documents (eg. PDF and DOC files). The ultimate edition is much faster searching for keywords.

If your xplorer² is slow and none of the above "natural" slow down reasons apply to your case, it could be that your antivirus is blocking xplorer² and won't let it function properly. If you use a 3rd party antivirus (other than Windows Defender) try adding xplorer² in the list of your AV whitelisted/trusted programs and see if it improves the situation.