When there is a text entry from user, you can set specific rules that the text must follow.
This can start off with simple limits, that are starting with the minimum and max lengths of text. This is available in the “Standard” type.
However, there are also many more advanced options that you can define when choosing “Custom” type.
In this case, you can specify which letters can be used (lowercase, uppercase or both) and what other characters can be allowed within the text. Starting with spaces, dashes, underscores, etc.
There is also an option to tick the “Allow empty” checkbox to allow leaving this question unanswered.
If you have more detailed requirements (eg for your own custom Barcodes), you can also use the “Advanced” type, which allows you to define your own regular expression. This is only recommended for people with a higher knowledge in setting and applying regular expressions.