Use pattern matching to validate fields

The matches pattern validation method ensures that the value of a field matches a specific pattern defined by a regular expression.

A regular expression is a special text string for describing a search pattern. We use these expressions to validate the text that an author enters into a field of an entry.

With a content type open for editing:

1. Select the text field you want to set a validation rule for and pick the Validation tab from the Field Settings panel.
2. Choose the required regular expression pattern you want to use from the Matches pattern dropdown, or define your own using the Custom option.
3. You can add an alternative validation message by entering it in the Validation message text box. This will be displayed if the field fails validation when published.

You can use the Custom option in the matches pattern dropdown to create your own. Using a handy library and expression checker, like Regular Expression 101, to test your expression makes things easier.

We've included some predefined expressions covering some standard scenarios.