regexp

Validates that a field value matches a regular expression.

Options

Option	Type	Default	Description
regexp	string | RegExp	required	The regular expression to match against
flags	string	""	Flags applied when regexp is a string (e.g. "i" for case-insensitive)
message	string	locale default	Custom error message

Playground

Valid values

Value	Notes
"abc123"	Matches ^[a-z0-9]+$
"my-slug"	Matches ^[a-z0-9-]+$

Invalid values

Value	Reason
"ABC!"	Uppercase and special char fail ^[a-z0-9]+$
"has space"	Space not in pattern

Notes

• Empty string ("") always returns valid: true — validators only run on non-empty values. Combine with notEmpty to require a value.
• regexp can be a string ("^[0-9]+$") or a RegExp literal (/^[0-9]+$/).
• flags only applies when regexp is a string; RegExp literals already carry their flags.