Keyboard Maestro uses ICU Regular Expressions (aka RegEx or RegExp) which is very similar to PCRE (Perl Compatible Regular Expressions), and you can read their documentation by choosing ICU Regular Expression Reference from the Help menu in Keyboard Maestro.
In Keyboard Maestro Actions, if the term “matches” is used, it means that it supports regular expression. However, there are many Actions in Keyboard Maestro where you can use a regular expression, which may not be obvious. For more info see Places where Regular Expressions can be used.
$nin the Action Replace box, where n is the number for the capture group.
$1, $2, $3
\nused in other apps/languages.
The ICU calls these modifiers “flag options”.
The search modifier “Pattern to Use” shown below is placed at the very beginning of the Search/Find Regular Expression box.
as shown in the below example #1.
|Purpose||Pattern to Use||Description|
|Global||NONE||All searches are global in Keyboard Maestro.
This is often indicated in other tools by the
|Case Insensitive||Matching will be in a case-insensitive manner.
In some Actions this is NOT necessary since the Action already provides an “ignoring case” option.
|Dot includes EOL||A “
|Multi-Line||Controls the behavior of “
If used, “
|Word Boundaries||Controls the behavior of \b in a pattern.
If used, word boundaries are found according to the definitions of word found in Unicode UAX 29, Text Boundaries.
|Comments||Ignores white space and allows #comments.
If used, white space within regular expressions is ignored and you can use #line-comments.
You can use Keyboard Maestro Text Tokens anywhere appropriate in both the Search pattern and the Replace pattern.
Example #1: Remove all line numbers from a string with multiple lines
Example #2: Extract Capture Group for Multiple Matches to Multiple Lines in a Variable
Sometimes you may need to extract a RegEx Capture Group after a match is made, and do this for multiple lines (matches) in the entire source string. To achieve this, you need to:
Both Actions can use the same RegEx pattern.
For a complete macro using this method, see:
MACRO: Get List of RegEx Capture Group of Multiple Matches