MaxLength

Checks if the number of characters in the value equals or is below the given maximum

since: Kirby 2.3.2
return (boolean)

This validator works like (sheet: validators/max) but it always checks for string length, even if a numeric value is given. The max validator will check for the value of the number in that case.

In your code

if(v::maxLength('Lorem ipsum dolor sit amet.', 10)) {
  echo 'Yay, valid!';
}

In fields

fields:
  example:
    label: Example field
    type: text
    validate:
      maxLength: 10