First, add the files whose file names you want to shorten to the list. You should not use the folder selection dialog "Add --> Folder". Instead add the parent folder(s) of the problem causing files by dragging and dropping them onto the program interface. As type to be imported, you can specify on request:"Read files and folders" as well as "Include all sub-folders".
The maximum number of 260 characters fully supported by Windows refers to the entire path (drive letter: \Folder 1\Folder 2\... \File name.extension) and not just the name, so it is important to add all parent folders with very long names. Alternatively, you can shorten the folder names first and subsequently the file names. This is particularly recommended if the folder structure to be processed is very extensive. In this case, define the type to be imported as "Read folders only" and "Include all sub-folders".
To improve the clarity of the current and new status of the name length, it is also helpful to display the following columns in the preview list:
To do this, click on the menu "List" and select the menu item "Customize columns...".
Rename Expert allows you to filter files to target only those files that contain too many character in the file name. Set, as shown in the figure, the maximum number of allowed characters in the path or file name and the program only shows only those files that matches the filter criterion in the preview list.
However, filtering out folders is only recommended in some cases. Normally, folders should not be filtered out because they contribute a large part to the path length. For example, if the names of the folders account for 80-90 percent of the path length, this is where the path length should be reduced. The tool for shortening the path length also only works optimally in most cases if files including the parent folders of several (or preferably all) levels have been added.
Click on the button featuring the "Plus" symbol to add the action "Other --> Shorten names" to the action list.
The picture shows the default configuration of the action. Folder and file names are limited to 64 characters. This setting is optional and can be changed at will. The option "Short file names individually to reach a path length of x characters" limits all file names to the set number of characters, depending on the total path length. This allows files from folders with fewer characters in the name to retain a longer name. The minimum length of the new file names can also be set.
Click on the button featuring the plus (+) symbol to add the action Remove to the action list.
The next step is to set the maximum number of characters allowed in file names. The settings shown in the figure would shorten all file names to 32 characters. File names which are already shorter than this length will remain unchanged.
To do this, select the Rename Function "Remove --> an area --> defined by character type" and make the settings shown in the illustration. Thereby, in this case, the file names will be limited to a maximum length of three words or groups of digits.
After cutting off characters, it is very likely that there are at least some names that would occur twice. The corresponding entries are given a red font color and can be viewed by clicking the Conflicts button in the lower status bar. To resolve these conflicts it is best to add the action Insert and select the conditional numbering there. This gives all folders and files with name collisions (within a folder) a consecutive numbering.
In the preview list, a preview of the new name of the file is displayed in real time. Potential conflicts such as duplicate file names, caused by the shortening, will be highlighted in red color and can be solved for example by the additional insertion of a conditional numbering at the end of the filename. Using the conditional numbering, a number is automatically inserted at the desired position (e.g., at the end of the file name), if the new file name is already taken by another new file name or a file with that name already exists.
If there are no conflicts, the Tasks dialog can now be opened by clicking on the Apply button. All files to be renamed are listed there and the renaming process can be started by a click on the Start button.