TypeScript's 1:1 validator, optimized from editor to runtime
ArkType is a runtime validation library that lets you define validators using native TypeScript type syntax instead of maintaining separate schema definitions. You write what looks like a TypeScript type, and ArkType generates an optimized validator that enforces those constraints at runtime. This eliminates the common pattern of duplicating type information across TypeScript interfaces and validation schemas like Zod or Yup.
The library was built to solve the performance and ergonomics problems inherent in existing validation solutions. By parsing type definitions ahead-of-time and compiling them into highly optimized validation functions, ArkType achieves dramatic performance improvements—benchmarks show it's 20-100x faster than Zod and over 2,000x faster than Yup for common validation operations.
ArkType is designed for developers who need to validate external data at application boundaries: API request/response payloads, form submissions, configuration files, or any scenario where untyped data enters your TypeScript application. With over 680,000 weekly downloads, it's increasingly adopted in production applications that require both type safety and high-throughput validation.
Beyond basic validation, ArkType 2.x introduced advanced features like pattern matching with the match function, which brings functional programming concepts to JavaScript with full type safety. The library's foundation in set theory allows it to reason about complex type relationships, handle discriminated unions intelligently, and provide introspectable validation logic that can be analyzed programmatically.
import { type } from 'arktype';
// Define a user validator with constraints
const User = type({
id: 'string.uuid',
username: 'string>2',
age: 'number>=18',
email: 'string.email',
role: "'admin'|'user'|'guest'",
metadata: {
'lastLogin?': 'Date',
'preferences?': {
theme: "'light'|'dark'",
notifications: 'boolean'
}
}
});
// Infer TypeScript type from validator
type User = typeof User.infer;
// Validate data from an API
const apiResponse = {
id: '550e8400-e29b-41d4-a716-446655440000',
username: 'john_doe',
age: 25,
email: 'john@example.com',
role: 'user',
metadata: {
lastLogin: new Date('2024-01-15'),
preferences: { theme: 'dark', notifications: true }
}
};
const result = User(apiResponse);
if (result instanceof type.errors) {
console.error('Validation failed:', result.summary);
// Detailed errors available in result.byPath
} else {
// result is typed as User
console.log(`Valid user: ${result.username}, age ${result.age}`);
}
// Pattern matching example
const Status = type("'pending'|'approved'|'rejected'");
const message = Status.match(
"'pending'", () => 'Awaiting review',
"'approved'", () => 'Request accepted',
"'rejected'", () => 'Request denied'
);
console.log(message('approved')); // 'Request accepted'API request validation: Validate incoming HTTP request bodies in Express, Fastify, or Next.js API routes to ensure data conforms to expected types before processing, with detailed error messages for client feedback.
Form data processing: Parse and validate user-submitted form data in React, Vue, or Svelte applications, handling string-to-number coercion, email format validation, and complex nested object structures with minimal boilerplate.
Configuration file parsing: Load and validate JSON/YAML configuration files at application startup, ensuring all required fields exist with correct types and constraints (like port numbers within valid ranges) before the app runs.
Database query results: Validate data returned from database queries or external APIs to catch schema mismatches early, especially useful when working with untyped database clients or third-party services that might change without notice.
Type-safe pattern matching: Use ArkType's match function to implement complex conditional logic based on discriminated unions or value patterns, replacing verbose if-else chains with declarative, optimized pattern matching that TypeScript can verify at compile time.
Superfast runtime validators with only one line
The modular and type safe schema library for validating structural data
Dead simple Object schema validation
TypeScript-first schema declaration and validation library with static type inference
npm install arktypepnpm add arktypebun add arktype