Prefix patterns

The pattern option takes any Python regular expression. It is tested with re.match against each path component, so it only has to describe the start of a name. Starting it with ^ makes that explicit.

Write patterns in single-quoted YAML strings with single backslashes.

Common formats

Pattern	Matches	Example source → URL
'^\d+--' (default)	Any number of digits, then --	123--file.md → file/
'^\d{3}--'	Exactly three digits, then --	001--file.md → file/
'^\d+-'	Digits, then one -	42-file.md → file/
'^\d+_'	Digits, then _	01_file.md → file/
'^[0-9]{2,4}-'	Two to four digits, then -	0001-file.md → file/

Three-digit prefixes only

plugins:
  - strip-number-prefix:
      pattern: '^\d{3}--'

010--intro.md becomes intro/. 10--intro.md does not match and keeps its prefix in the URL. Use this to make sure all names use the same width.

Single-dash prefixes

plugins:
  - strip-number-prefix:
      pattern: '^\d+-'

01-intro.md becomes intro/. Be careful with names that start with a number as part of the title, such as 2024-review.md: it becomes review/. The double dash in the default pattern avoids that.

Patterns that end in a dot do not work

plugins:
  - strip-number-prefix:
      pattern: '^\d+\.'   # does not clean URLs

With 1.intro.md, the plugin detects the prefix, but the URLs stay 1.intro/. When the plugin cleans dest_path and url, it treats the text after the last dot of a component as a file extension and applies the pattern to the part before it. For the URL component 1.intro, that part is 1, which does not match ^\d+\.. Use a separator other than ., such as --, - or _.

Choosing a pattern

• Keep one pattern for the whole project. The plugin has one pattern option and applies it everywhere.
• Prefer a separator that does not occur naturally at the start of names. -- is a good choice.
• After changing the pattern, run mkdocs build --strict. A pattern that is too broad can make two pages collide, and strict mode reports it.