There are three overall type of filters you can use to control a Folder Compare session's scope: File Filters that include or exclude files based on their name or attributes, Display Filters that show or hide lines of the comparison based on comparison status, and Folder Display Filters that control when folders appear.
For instance, you can set the display filter to View > Show Left Newer 
to display only those files that are newer on the left side of the comparison. Or you can set a file filter to exclude *.bak files if you don't want to see or manipulate them.
By default, commands that act on a selected folder's contents (such as Copy, Move, Delete, etc.) will respect the current filters. That is, if the selection includes a folder, the folder's filtered-out contents are skipped. To change this default behavior, pick Tools > Options 
, switch to the File Operations page, and mark the Include hidden items by default checkbox. In either case, action dialogs allow you to override the default behavior on a case-by-case basis.
Pick View > Suppress Filters 
to temporarily suppress file filters and display filters. Files and folders that were hidden will appear colored teal (blue-green) and can be processed.
File Filters
You can specify the type of files you want to include in (or exclude from) the session. For instance, if you are comparing Delphi projects you could include file types such as *.pas, *.dfm, and *.dpr. Or, you could include all files except *.dcu and *.~* by excluding these file types.
To specify a simple "include these types" filter, use the Filters toolbar edit. Enter the file types separated by semicolons, or use the dropdown list to select from presets. Include a minus sign (-) in front of files to be excluded.
In addition to these simple wildcard filters, you can specify more complex filters that include or exclude files or folders by name. Pick Session > Session Settings 
, and switch to the Name Filters tab. Or, simply click the Filters 
toolbar button.
Files can also be filtered based on their modified date, size, file attributes or text content. In the Session Settings dialog, switch to the Other Filters tab. (Folders are not directly filtered based on their attributes, but are affected by the filtering of their contents.)
Display Filters
Display filters limit the view to certain comparison results. The comparison results are determined by the session's comparison rules. For instance, you can pick View > Show Differences 
to remove all the matching files so that you can concentrate on the mismatches.
Folder Display Filters
By default, folders only appear if at least one file they contain is visible. However, you can switch to one of the other folder display filters.
View > Always Show Folders 
causes all folders to appear (unless they have been explicitly excluded by file filters), regardless of the other display filter selection.
View > Compare Files and Folder Structure 
causes folders to respect the display filters. For example, if the main display filter is Show All 
then all folders appear. If it is Show Orphans 
, only orphan folders and folders that contain orphan files are shown.
View > Only Compare Files 
suppresses all empty folders, both truly empty folders and folders whose entire contents are hidden by other display or file filters.
View > Ignore Folder Structure 
hides the folder tree and aligns files regardless of what subfolder they are in.
See also