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Bootstrap 5 Form Validations

Form validation is "the technical process by which a web form verifies the accuracy of the user's input." The form will either notify the user of their error or require them to correct it. It will allow a user to show validation in advance. The form is genuine, and users are permitted to proceed with their user interaction.

Initially, the form validation function verifies that all required fields contain data. It only takes a bootstrap 5 form validation classes to traverse each form field and check for data. Second, the entered data must be validated for correct form and value.


The following syntax helps to create validation in the form using bootstrap 5 classes.

How to bootstrap 5 form validation works

Here's how Bootstrap 5 form validation works:

  • CSS's two pseudo-classes which are the ": invalid" and ":valid" use to validate HTML forms. It applies to the elements <input>, <select>, and <textarea>.
  • Bootstrap 5 applies the ":invalid" and ":valid" styles to the parent "was-validated" class. The "was-validated" class often associates with the <form> element. Every necessary field without a value is displayed as invalid upon page load. Thus, we can select validation after form submission.
  • After submission, the ".was-validated" class removes validation from the <form> element to reset the form's appearance.
  • As a fallback, the ".is-invalid" and the ".is-valid" classes may be used for server-side validation instead of the pseudo-classes.
  • Due to CSS limitations, it is currently unable to apply styles to a DOM <label> that precedes a form control without using custom JavaScript.
  • The constraint validation API, a collection of JavaScript methods for validating form controls, is supported by all modern browsers.
  • Feedback messages may use either the browser defaults or our bespoke feedback styles with additional HTML and CSS.
  • JavaScript's setCustomvalidity function allows for custom validation messages.

Registration form Example

The following example shows text, number, email, textarea, and checkbox input element with form validation. We can create registration form with user name, email, mobile number, and message data fields. The input field assigns form validation class using the <div> tag.


The below image shows the registration form with validation.

Bootstrap 5 Form Validations

Login form Example

The following example shows text, email with form validation. We can create login form with email and password input fields.


The below image shows login form with validation.

Bootstrap 5 Form Validations


This function creates user interactive and valid form in the web page using bootstrap 5 classes. Bootstrap 5 form validation helps to fill mandatory fields by the users. The invalid message displays in a red text by default. After entering the correct data form field becomes valid.

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