Code folding allows you to hide parts of a document in the editor, making it easier to overview large documents. In KatePart the foldable regions are calculated using rules defined in the syntax highlight definitions, and therefore it is only available in some formats - typically program source code, XML markup and similar. Most highlight definitions supporting code folding also lets you manually define foldable regions, typically using the BEGIN and END keywords.

To use the code folding feature, activate the folding markers using View → Show Folding Markers menu item if they are not already visible. The Folding Markers Pane on the left side of the screen displays a graphical view of the foldable regions, with triangle symbols to indicate the possible operation on a given region: a top down triangle means that the region is expanded, clicking it will collapse the region and a right pointing triangle will be displayed instead.

Three commands are provided to manipulate the state of folding regions, see the menu documentation.

The folded lines are remembered when a file is closed, so when you reopen the file the folded nodes will still be folded. This applies to reload operations as well.

If you do not want to use the code folding feature, you can disable the Show folding markers (if available) option in the Appearance page of the editor configuration.