arktype

ArkType

Runtime validation with TypeScript-like syntax. 100x faster than Zod.

Installation

npm install arktype

Requires TypeScript >=5.1, "type": "module" in package.json, and strict or strictNullChecks in tsconfig.

Core Syntax

import { type } from "arktype";

const User = type({
  name: "string",
  email: "string.email",
  "age?": "number >= 0", // optional with constraint
  role: "'admin' | 'user'", // literal union
  tags: "string[]", // array
});

type User = typeof User.infer; // extract TS type

// Validation
const result = User(inputData);
if (result instanceof type.errors) {
  console.error(result.summary); // human-readable errors
} else {
  console.log(result.name); // narrowed to User
}

String Keywords

Primitives: string, number, boolean, bigint, symbol, null, undefined, object, unknown, never

String subtypes: string.email, string.uuid, string.uuid.v4, string.url, string.json, string.json.parse (morph), string.numeric, string.numeric.parse (morph), string.integer, string.date, string.date.parse (morph), string.semver, string.ip, string.base64, string.trim (morph), string.lower (morph), string.upper (morph)

Number subtypes: number.integer, number.positive, number.negative, number.safe, number.epoch

Instanceof: Date, Error, RegExp, Map, Set, Promise, Array, FormData, File, Blob

Constraints

// Numbers
"number > 0"; // exclusive min
"number >= 0"; // inclusive min
"0 < number <= 100"; // range
"number % 2"; // divisible by

// Strings (length)
"string > 0"; // non-empty
"1 <= string <= 50"; // length range

// Arrays (length)
"string[] > 0"; // non-empty array

// Dates
"Date > d'2000-01-01'"; // after date literal

// Regex
"/^[a-z]+$/"; // pattern

Objects

type({
  required: "string",
  "optional?": "number", // optional
  withDefault: "string = 'hi'", // default value
  "[string]": "unknown", // index signature
  "+": "reject", // error on undeclared keys (or "delete" to strip)
});

// Merge objects
const Extended = Base.merge({ extra: "string" });
// or: type({ "...": Base, extra: "string" })