The Comment and Uncomment commands, available from the Tools menu allow you to add or remove comment markers to the selection, or the current line if no text is selected, if comments are supported by the format of the text you are editing.

The rules for how commenting is done are defined in the syntax definitions, so if syntax highlighting is not used, commenting/uncommenting is not possible.

Some formats define single line comment markers, some multiline markers and some both. If multiline markers are not available, commenting out a selection that does not fully include its last line is not possible.

If a single line marker is available, commenting single lines is preferred where applicable, as this helps to avoid problems with nested comments.

When removing comment markers, no uncommented text should be selected. When removing multiline comment markers from a selection, any whitespace outside the comment markers is ignored.

To place comment markers, use the Tools → Comment menu item or the related keyboard shortcut sequence, default is Ctrl+D.

To remove comment markers, use the Tools → Uncomment menu item or the related keyboard shortcut, default is Ctrl+Shift+D.