# Class Validator Documentation

> class-validator is a TypeScript/JavaScript validation library that uses decorator and non-decorator based validation, powered by validator.js, and works in both browser and Node.js.

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## Getting Started

- [Installation](https://class-validator.sonicar.tech/installation/): Requirements, `npm install class-validator`, and enabling `experimentalDecorators` in tsconfig.json.
- [Basic Usage](https://class-validator.sonicar.tech/usage/): Creating a validated class, calling `validate()` / `validateSync()`, and validation options.

## Validation

- [Validation Decorators](https://class-validator.sonicar.tech/decorators/): Overview of the common and type validation decorators.
- [Validation Messages](https://class-validator.sonicar.tech/messages/): Custom messages, message variables ($value, $property, $constraint1…), and dynamic message functions.
- [Validating Arrays](https://class-validator.sonicar.tech/arrays/): The `each: true` option and array-specific decorators like `@ArrayMinSize`.
- [Validating Nested Objects](https://class-validator.sonicar.tech/nested-objects/): `@ValidateNested()` for single objects, arrays of objects, and deep nesting.
- [Validating Promises](https://class-validator.sonicar.tech/promises/): `@ValidatePromise()` for properties holding a `Promise`-returned value.
- [Inheriting Validation Decorators](https://class-validator.sonicar.tech/inheritance/): How decorators are inherited and combined across subclasses.
- [Conditional Validation](https://class-validator.sonicar.tech/conditional/): `@ValidateIf()` to skip validators when a condition function returns false.

## Advanced

- [Whitelisting](https://class-validator.sonicar.tech/whitelisting/): Stripping or forbidding properties that have no decorators.
- [Passing Context to Decorators](https://class-validator.sonicar.tech/context/): Attaching custom metadata to a `ValidationError`.
- [Validation Groups](https://class-validator.sonicar.tech/groups/): Using different validation schemas for the same class.
- [Custom Validation](https://class-validator.sonicar.tech/custom-validation/): Writing custom constraint classes and custom decorators.
- [Using Service Container](https://class-validator.sonicar.tech/service-container/): Dependency injection into validator constraints via TypeDI.

## API Reference

- [Validation Decorators Reference](https://class-validator.sonicar.tech/validation-decorators/): Full list of built-in decorators grouped by category (common, type, number, date, string, array, object).
- [Manual Validation](https://class-validator.sonicar.tech/manual-validation/): Non-decorator validation functions and sync vs. async validation.

## About

- [About Sonicar Tech](https://class-validator.sonicar.tech/about-sonicar-tech/): Who built and maintains this documentation, and what Sonicar Tech does.
- [Sonicar Tech LLC](https://sonicar.tech): Documentation-as-code agency — get professional docs for your product shipped in 1 week.