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 03 2026
1. Custom HTML5 Form Validator In Vanilla JavaScript – 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 the Bootstrap framework.
Features:
- small size and zero dependencies
- no need to change your HTML
- a wide range of pre-defined rules
- custom rules
- support plugins
- custom styles and css classes for invalid fields and error messages
- custom messages
- showing tooltips as error messages
- custom places for the error labels
- localization (defining error messages for different languages)
- user-friendly setup: console warning messages if something incorrect
- written in Typescript and good test coverage
2. Bootstrap Form Validation Library Without jQuery – Native Validator
A vanilla JavaScript-powered form validation library for the latest bootstrap framework, without jQuery dependency.
3. 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.
Features:
- Custom trigger event: blur, click, change, etc.
- Allows you to validate form fields using custom regex.
- Pretty and interactive feedbacks for invalid form fields.
- Supports multi fields. Suitable for credit card form validation.
- With no dependencies.
4. Minimal HTML5 Form Validator In Vanilla JavaScript – 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.
5. Regex Based Form Validator For Bootstrap 5
A script that demonstrates how to validate form fields in your Bootstrap 5 project by using custom Regex.
6. Client-Side Declarative Form Validation using Strictly.js
A JavaScript library that handles client-side form validation with minimal configuration.
Features:
- HTML Attribute-Based Rules: Define validation directly in your markup (
data-strictly-*). - Real-time Feedback: Validate as users type (
oninput) or just show errors (showerror). - Customizable Errors: Control error message placement, tag (
div/p), and CSS classes. - Wide Input Support: Handles text, email, numbers (integer, digits, decimal), checkboxes, radio buttons, textareas, and select elements.
- Advanced Validation Rules: Includes regex pattern matching, password complexity enforcement, and field comparison
- Pattern & Password Validation: Supports regex and configurable password complexity rules.
- Checkbox/Select Counts: Enforce min/max selections for checkboxes (by name) and multi-selects.
- Length Constraints: Validate min/max characters or words.
- Field Matching: Ensure one field’s value equals another (
data-strictly-equalto). - Dynamic Element Handling: Automatically picks up and validates form fields added to the DOM later.
- Detailed Validation Reports: Get comprehensive validation results including errors and form values.
7. Beginner-Friendly JavaScript Form Validation Library – Trivule
A JavaScript library designed to simplify form validation. It’s perfect for both beginners and experienced developers.
You can quickly add validation rules to form fields using simple HTML attributes. There is no need to write complex JavaScript code from scratch; Trivule takes care of it for you.
Trivule provides real-time feedback as users fill out the form fields. You can validate entire forms or specific inputs, and customize feedback messages to suit your needs. Trivule also supports multiple languages and allows you to disable the submit button until all fields are valid.
8. Extend HTML5 Form Validation With Custom Rules And Errors – Bouncer.js
The Bouncer.js JavaScript library is created to extend the native HTML5 form validation that enabling customizable form validation on the form fields.
Features:
- Validate form fields on submit, blur and data change.
- Custom validation rules.
- Easy to add your own validators.
- Custom error messages.
- Useful API methods and events.
9. Fast Client-side Form Validation with Zephyr Form Validator
A lightweight JavaScript library for fast, customizable, client-side form validation.
It features real-time error feedback, custom validation rules, and CSS class toggling for visual states.
10. Feature-rich Form Validation Library – OctaValidate
An open-source, feature-rich form validation JavaScript library that makes it easy to validate form input against built-in rules, regular expressions, and input attributes. It can help you validate the HTML forms in your application to increase user engagement by providing grouped errors, it can also help you make your forms manageable and consistent across many devices and browsers.
More Resources:
Looking for more JavaScript solutions to validate form fields on modern web applications? Here are some resources you might find useful: