About

This page is about form validation in HTML.

The javascript counterpart is called the constraint validation API ¹⁾.

In short, you set standard HTML attributes that constrain the possible value of form elements.

Example

Check email

List of validation rules

• required
• min
• max
• minLength
• maxLength
• pattern
• validate

Limitations

HTML validation has its limitations.

• it only works in the browser (not React Native, …)
• it's hard/impossible to show custom error messages to our user.

Function

• form.checkValidity() - Returns true if the form's controls are all valid; otherwise, returns false.
• form.reportValidity() - Returns true if the form's controls are all valid; otherwise, returns false and informs the user.

Documentation / Reference

• https://developer.mozilla.org/en-US/docs/Learn/HTML/Forms/Form_validation