Flutter Validators

The most comprehensive string validation package for Dart & Flutter.

Inspired by validator.js · 20+ validators · Works with Flutter Forms out of the box

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A pure Dart package with 20+ string validators and sanitizers, from emails and URLs to credit cards and UUIDs. Use them as simple functions, convenient String extensions, or plug them directly into Flutter's TextFormField with the built-in Validator class. Zero dependencies, fully tested.

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📦 Installation

dependencies:
  flutter_validators: ^1.1.0

Then run:

dart pub get

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🚀 Quick Start

import 'package:flutter_validators/flutter_validators.dart';

Use as String Extensions

'foo@bar.com'.isEmail;        // true
'https://google.com'.isURL;   // true
'4111111111111111'.isCreditCard; // true
'abc123'.isAlphanumeric;      // true

Use as Top-Level Functions

isEmail('foo@bar.com');       // true
isURL('https://google.com'); // true
isIP('192.168.1.1');         // true

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📝 Flutter Form Integration

The Validator class returns String? Function(String?) closures — exactly what TextFormField.validator expects. Each method accepts a custom errorMessage.

Form(
  child: Column(
    children: [
      TextFormField(
        decoration: const InputDecoration(labelText: 'Email'),
        validator: Validator.email(errorMessage: 'Enter a valid email'),
      ),
      TextFormField(
        decoration: const InputDecoration(labelText: 'Website'),
        validator: Validator.url(),
      ),
      TextFormField(
        decoration: const InputDecoration(labelText: 'Age'),
        validator: Validator.numeric(errorMessage: 'Must be a number'),
      ),
    ],
  ),
)

Tip: Use Validator.required() alongside other validators to enforce non-empty fields.

See the example/ directory for a complete working app.

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📋 All Validators

Every validator is available both as a top-level function and as a String extension.

Validator	Extension	Description
isEmail(str)	str.isEmail	Valid email address
isURL(str)	str.isURL	Valid HTTP/HTTPS URL
isIP(str, [version])	str.isIP / str.isIPv4 / str.isIPv6	Valid IP address (v4 or v6)
isUUID(str)	str.isUUID	Valid UUID
isCreditCard(str)	str.isCreditCard	Credit card number (Luhn algorithm)
isDate(str)	str.isDate	Parseable date string
isJson(str)	str.isJson	Valid JSON
isInt(str)	str.isInt	Valid integer
isNumeric(str)	str.isNumeric	Valid number (int or float)
isAlpha(str)	str.isAlpha	Letters only (a–z, A–Z)
isAlphanumeric(str)	str.isAlphanumeric	Letters and numbers only
isAscii(str)	str.isAscii	ASCII characters only
isBase32(str)	str.isBase32	Base32 encoded
isBase58(str)	str.isBase58	Base58 encoded
isBoolean(str)	str.isBoolean	Boolean string (true/false/1/0)
isHexColor(str)	str.isHexColor	Hex color code (#fff, ff0000)
isPhone(str)	str.isPhone	Valid phone number
isLength(str, min, [max])	str.isLength(min, [max])	Length within range
equals(str, comparison)	str.equals(comparison)	Exact string match

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🏗️ Form Validator API Reference

All methods on the Validator class return String? Function(String?):

Validator.required({String errorMessage})
Validator.email({String errorMessage})
Validator.url({String errorMessage})
Validator.ip({int? version, String errorMessage})
Validator.date({String errorMessage})
Validator.numeric({String errorMessage})
Validator.integer({String errorMessage})
Validator.alpha({String errorMessage})
Validator.alphanumeric({String errorMessage})
Validator.phone({String errorMessage})
Validator.creditCard({String errorMessage})
Validator.json({String errorMessage})
Validator.uuid({String errorMessage})
Validator.hexColor({String errorMessage})
Validator.ascii({String errorMessage})
Validator.base32({String errorMessage})
Validator.base58({String errorMessage})
Validator.boolean({String errorMessage})
Validator.equals(String comparison, {String errorMessage})
Validator.length(int min, {int? max, String errorMessage})

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🤝 Contributing

Contributions, issues, and feature requests are welcome! Feel free to check the issues page.

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📄 License

This project is MIT licensed.