Validator.js — String Validation and Sanitization for JavaScript

Introduction

Validator.js is a library of string validators and sanitizers for JavaScript. It runs in both Node.js and browser environments, giving you a single dependency for checking emails, URLs, UUIDs, credit card numbers, and many more common formats.

What Validator.js Does

• Validates over 80 string formats including email, URL, IP, UUID, and ISO dates
• Sanitizes input by trimming, escaping HTML, normalizing emails, and stripping low bytes
• Works in Node.js and the browser with zero external dependencies
• Provides locale-aware validation for phone numbers, postcodes, and tax IDs
• Supports custom validation by composing built-in checks

Architecture Overview

Validator.js is a pure-function library with no classes or state. Each validator and sanitizer is an independent function that takes a string and returns a boolean or transformed string. The library ships as a single ES module with tree-shakeable named exports, keeping bundle size small when you import only what you need.

Self-Hosting & Configuration

• Install via npm, yarn, or pnpm for Node.js projects
• Import individual validators to reduce bundle size in frontend builds
• No configuration files are needed as each function is self-contained
• Use the sanitizer functions at your API boundary before storing user input
• Pair with schema libraries like Zod or Yup for object-level validation

Key Features

• Over 80 built-in validators covering common web input patterns
• Locale-specific checks for phone numbers and postal codes across 50+ countries
• Lightweight with zero dependencies and a small bundle footprint
• Consistent API where every function takes a string and options object
• Active maintenance with regular updates for new validation rules

Comparison with Similar Tools

• Zod — validates typed objects and schemas; Validator.js focuses on raw string checks
• Yup — schema-based with async support; Validator.js is synchronous string-only
• joi — Hapi ecosystem schema validator; Validator.js is framework-agnostic
• class-validator — decorator-based for TypeScript classes; Validator.js uses plain functions
• Valibot — modular schema builder; Validator.js is a flat collection of string utilities

FAQ

Q: Can I use Validator.js in the browser? A: Yes. It ships as an ES module and works in any modern browser or bundler.

Q: Does it validate objects or only strings? A: Only strings. For object validation, pair it with a schema library.

Q: Is it safe to rely on for security-critical input? A: It is widely used for input sanitization, but always combine it with server-side checks and parameterized queries.

Q: How do I add a custom validator? A: Compose existing validators in a wrapper function; the library does not have a plugin API.

Sources

• https://github.com/validatorjs/validator.js
• https://www.npmjs.com/package/validator