hugo/docs/content/en/functions/strings/ToLower.md

title	linkTitle	description	categories	keywords	menu	function	relatedFunctions	aliases
strings.ToLower	lower	Converts all characters in the provided string to lowercase.	functions		docs parent functions	aliases returnType signatures lower string strings.ToLower INPUT	strings.FirstUpper strings.Title strings.ToLower strings.ToUpper	/functions/lower

Note that lower can be applied in your templates in more than one way:

{{ lower "BatMan" }} → "batman"
{{ "BatMan" | lower }} → "batman"