Using these attributes will show validation errors, or limit what the user can enter into an <input>.

If you would like to make “empty” include values that consist of spaces only, you can add the attribute pattern=.*\S.*.

Currently, there is no way to style those little validation tooltips.

Website: <input type="url" name="website" required pattern="https?://.+"> Now our input box will only accept text starting with http:// or https:// and at least one additional character

var applicationForm = document.getElementById("applicationForm"); if (applicationForm.checkValidity()) { applicationForm.submit(); } else { applicationForm.reportValidity(); }

These all come from the HTML Standard.

setCustomValidity

Note that we added HTML validation with specifying the types of the field (email and password). This allows the browser to validate the input.

Constraints

The bindings are two-way because any HTML5 contraint validation errors will be added to the Final Form state, and any field-level validation errors from Final Form will be set into the HTML5 validity.customError state.