The native HTML5 validation feature is not enough.
We also recommend you use a JavaScript library to extend and enhance the default form validation functionalities for better user experiences on modern web design.
In this post, you’ll find a list of the 10 best and most downloaded JavaScript Form Validation libraries (without any 3rd dependencies such as jQuery) to validate your HTML form with custom error messages, CSS styles, validation rules, and more. Enjoy.
Originally Published Feb 10, 2018, updated Jan 20 2023
1. validator.js
Lightweight JavaScript form validation, that had minimal configuration and felt natural to use. No dependencies, support UMD.
2. Pristine
Pristine is a lightweight vanilla JavaScript form validation library which works with the native HTML5 attributes and allows you to create your own validators of course.
3. facile-validator

Laravel-inspired validation for HTML forms, built for simplicity of use.
4. Bouncer.js
The Bouncer.js JavaScript library is created to extend the native HTML5 form validation that enables the customizable form validation on the form fields.
5. Just-validate
Just-validate is a dependency-free, HTML5 data attribute based form validation that supports both client side and server side form validation. Validation rules are fully customizable via JavaScript. Compatible with Bootstrap framework.
6. Fast User-friendly Form Validation Plugin – Validator.js
A fast, cross-browser, user-friendly, highly customizable form validator that works with the native HTML5 input types: text, email, url, date, etc.
7. Vanilla JavaScript Form Validator For Bootstrap 5/4/3 Framework

A vanilla JavaScript plugin that adds extensible form validation functionalities to your Bootstrap project without third-party JS libraries like jQuery.
8. fonk
A framework agnostic form schema validation library.
9. Inspect
Form validation in Javascript Vanilla, without dependencies and multiple languages. ~8kb.
10. ValidForm
ValidForm is a thin JavaScript wrapper on the HTML5 Form Validation features. It is very small at about 200 lines of code (7k, 5.6k compressed), and it has no dependencies.
More Resources:
Looking for more JavaScript solutions to validate form fields on modern web applications? Here are some resources you might find useful: