zod vs joi vs yup vs io-ts
Type Validation Libraries Comparison
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What's Type Validation Libraries?

Type validation libraries are essential tools in web development that help ensure data integrity by validating the structure and types of data at runtime. These libraries provide mechanisms to define schemas, validate incoming data against those schemas, and return meaningful error messages when validation fails. They are particularly useful in applications that rely on external data sources, such as APIs, where data may not always conform to expected formats. By using these libraries, developers can catch errors early in the development process, improve code reliability, and enhance overall application security.

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zod31,436,13538,3991.62 MB5956 hours agoMIT
joi12,236,11521,107531 kB190a year agoBSD-3-Clause
yup7,582,35323,395260 kB2466 months agoMIT
io-ts1,990,0266,779460 kB1646 months agoMIT
Feature Comparison: zod vs joi vs yup vs io-ts

TypeScript Integration

  • zod:

    Zod is designed with TypeScript in mind, providing a seamless experience for defining and validating types. It allows you to infer types directly from your schemas, ensuring type safety throughout your application.

  • joi:

    Joi does not have built-in TypeScript support, but it can be used with TypeScript with some additional type definitions. However, it may not provide the same level of type safety as io-ts or Zod when it comes to runtime validation.

  • yup:

    Yup has good TypeScript support, allowing you to define schemas with types that can be inferred. This makes it easier to work with TypeScript in projects that require validation, especially in form handling.

  • io-ts:

    io-ts provides excellent integration with TypeScript, allowing you to define runtime types that match your TypeScript types. This ensures that your data validation is type-safe and that any discrepancies between expected and actual data types are caught at runtime.

Validation Flexibility

  • zod:

    Zod focuses on simplicity and speed, providing a minimalistic API for defining schemas. It supports basic validation rules and is designed to be easy to use, making it ideal for projects that require quick and efficient validation.

  • joi:

    Joi is known for its expressive and flexible schema definitions, enabling developers to create complex validation rules easily. It supports a wide range of validation scenarios, including conditional validations and custom error messages.

  • yup:

    Yup provides a straightforward API for defining validation schemas, making it easy to implement basic and advanced validation rules. It is particularly effective for form validation, where you can define schemas that correspond to form fields.

  • io-ts:

    io-ts offers a functional approach to validation, allowing you to compose complex validation logic using combinators. This flexibility makes it suitable for applications with intricate validation requirements.

Error Handling

  • zod:

    Zod provides concise error messages that indicate what went wrong during validation. While it may not be as detailed as io-ts or Joi, it offers a straightforward approach to error handling that is easy to understand.

  • joi:

    Joi offers comprehensive error messages that can be customized to provide clear feedback on validation failures. It allows developers to define specific error messages for different validation rules, enhancing the user experience.

  • yup:

    Yup provides user-friendly error messages that can be easily customized. It allows you to define specific error messages for each validation rule, making it suitable for form validation where clear feedback is essential.

  • io-ts:

    io-ts provides detailed error messages that include information about the expected and actual types, making it easier to debug validation issues. The error handling mechanism is designed to be informative and helpful for developers.

Learning Curve

  • zod:

    Zod is designed to be simple and straightforward, making it easy to learn and use. Its minimalistic approach allows developers to quickly grasp its concepts and implement validation without much overhead.

  • joi:

    Joi is relatively easy to learn, especially for developers familiar with schema-based validation. Its expressive syntax allows for quick adoption, but mastering its full capabilities may take time.

  • yup:

    Yup is known for its simplicity and intuitive API, making it easy for developers to get started with validation. Its learning curve is gentle, especially for those working with forms in React.

  • io-ts:

    io-ts has a steeper learning curve due to its functional programming style and the need to understand TypeScript's type system. However, once mastered, it offers powerful capabilities for type-safe validation.

Performance

  • zod:

    Zod is highly performant, focusing on speed and efficiency. Its lightweight design ensures that validation checks are fast, making it ideal for applications that require rapid validation.

  • joi:

    Joi is generally performant, but complex schemas with many validation rules can lead to slower validation times. It is important to optimize schema definitions for performance-critical applications.

  • yup:

    Yup is designed for performance and is particularly efficient in client-side validation scenarios. Its lightweight nature allows for quick validation, making it suitable for real-time form validation.

  • io-ts:

    io-ts may have performance overhead due to its functional nature and runtime type checking. However, it is optimized for TypeScript, which can mitigate some performance concerns in type-heavy applications.

How to Choose: zod vs joi vs yup vs io-ts
  • zod:

    Choose Zod if you want a lightweight and TypeScript-first validation library that emphasizes speed and simplicity. Zod is designed for modern TypeScript applications and offers a clear and concise API, making it easy to define and validate schemas without unnecessary complexity.

  • joi:

    Select Joi if you prefer a schema-based validation approach that is highly expressive and flexible. Joi is well-suited for server-side applications, especially with Node.js, and offers a rich set of validation rules and customization options, making it ideal for complex validation scenarios.

  • yup:

    Opt for Yup if you are looking for a simple and intuitive API for schema validation, especially in client-side applications. Yup is particularly popular in form validation scenarios and integrates well with libraries like Formik, providing a straightforward way to handle validation in React applications.

  • io-ts:

    Choose io-ts if you need a library that integrates seamlessly with TypeScript's type system, allowing you to define runtime types that correspond directly to your TypeScript types. It is particularly useful for projects that require strict type checking and want to leverage functional programming paradigms.

Similar Npm Packages to zod

zod is a TypeScript-first schema declaration and validation library. It allows developers to define schemas for their data structures and validate data against these schemas in a type-safe manner. Zod is particularly useful for ensuring that the data conforms to expected formats, making it a great choice for applications that require robust data validation. While Zod offers a powerful solution for schema validation, there are several alternatives in the ecosystem that provide similar functionalities. Here are a few notable alternatives:

  • io-ts is a runtime type system for TypeScript that allows you to define types and validate data at runtime. It provides a functional approach to validation and can be integrated with other libraries like fp-ts for functional programming paradigms. io-ts is particularly useful for applications that require both static type checking and runtime validation, making it a solid choice for developers who prioritize functional programming principles.

  • joi is a powerful schema description language and data validator for JavaScript objects. It provides a rich set of features for defining complex validation rules and is widely used in Node.js applications. Joi's expressive syntax allows developers to create detailed validation schemas with ease. If you are looking for a mature and feature-rich validation library that works well in both client-side and server-side applications, joi is an excellent option.

  • yup is a JavaScript schema builder for value parsing and validation. It is heavily inspired by Joi but is designed to work seamlessly with React and other modern JavaScript frameworks. Yup provides a simple and intuitive API for defining validation schemas and supports asynchronous validation. If you are building applications with React and need a validation library that integrates well with form libraries like Formik, yup is a great choice.

To see how zod compares with io-ts, joi, and yup, check out the comparison: Comparing io-ts vs joi vs yup vs zod.

Similar Npm Packages to joi

joi is a powerful schema description language and data validator for JavaScript objects. It allows developers to define complex validation rules for their data structures, making it easier to ensure that incoming data meets specific criteria before processing it. Joi is particularly useful in server-side applications, where data validation is crucial for maintaining data integrity and security. While joi is a popular choice for data validation, there are several alternatives available in the ecosystem. Here are a few notable ones:

  • celebrate is a middleware for Express.js that integrates Joi for validating request data. It allows developers to define validation schemas for request parameters, query strings, and request bodies, making it easy to enforce data integrity in Express applications. Celebrate simplifies the validation process by providing a straightforward API that works seamlessly with Express, ensuring that only valid data reaches your route handlers. If you're already using Joi and want to integrate it into your Express application, Celebrate is an excellent choice.
  • express-validator is another popular middleware for validating and sanitizing request data in Express applications. Unlike Joi, which focuses on schema-based validation, express-validator uses a set of validation and sanitization middlewares that can be applied to individual routes. This flexibility allows developers to define validation rules directly in their route definitions. If you prefer a more modular approach to validation and want to keep your validation logic close to your route handlers, express-validator is a great alternative.
  • yup is a JavaScript schema builder for value parsing and validation. It is similar to Joi but offers a more modern API and is often favored for its promise-based validation and support for asynchronous validation. Yup is particularly useful for client-side validation in React applications, but it can also be used in server-side contexts. If you're looking for a lightweight and flexible validation library that works well with both client and server applications, Yup is worth considering.

To explore how joi compares with celebrate, express-validator, and yup, check out the comparison: Comparing celebrate vs express-validator vs joi vs yup.

Similar Npm Packages to yup

yup is a JavaScript schema builder for value parsing and validation. It is often used in conjunction with form libraries to ensure that user input meets certain criteria before being processed. Yup provides a fluent API for defining schemas, making it easy to validate complex data structures. While yup is a popular choice for validation, there are several alternatives available in the JavaScript ecosystem. Here are a few notable ones:

  • express-validator is a set of middleware functions that can be used to validate and sanitize user input in Express.js applications. It is built on top of validator.js and provides a simple way to validate request data, such as query parameters, body data, and headers. If you're working with an Express application and need to validate incoming requests, express-validator is a robust solution that integrates seamlessly with the Express framework.
  • joi is another powerful schema description language and data validator for JavaScript. It allows developers to create complex validation rules and provides a rich set of features for validating various data types. Joi is particularly useful for server-side validation in Node.js applications, and it can be used to validate incoming request data as well as data from other sources. If you need a comprehensive validation library that supports complex validation scenarios, joi is an excellent option.
  • validator.js is a library that provides a set of string validators and sanitizers. While it does not offer the same schema-based validation approach as yup, joi, or express-validator, it can be used in conjunction with other libraries to perform basic validation tasks. If you need lightweight validation functions for specific use cases, validator.js can be a useful addition to your toolkit.

For a detailed comparison of these validation libraries, check out the following link: Comparing express-validator vs joi vs yup.

Similar Npm Packages to io-ts

io-ts is a TypeScript library for runtime type validation and decoding. It allows developers to define types using a functional approach and validate data at runtime, ensuring that the data conforms to the specified types. This is particularly useful in scenarios where data comes from external sources, such as APIs, and needs to be validated before use. io-ts integrates seamlessly with TypeScript, providing strong type inference and ensuring type safety throughout your application.

While io-ts offers a robust solution for runtime type validation, there are several alternatives in the ecosystem that also provide similar functionality. Here are a few noteworthy options:

  • joi is a powerful schema description language and data validator for JavaScript objects. It allows developers to create complex validation rules and provides a rich set of features for validating and sanitizing data. joi is widely used in Node.js applications and is known for its expressive syntax and flexibility. If you are looking for a comprehensive validation library that can handle complex validation scenarios, joi is an excellent choice.

  • runtypes is a library for creating runtime type checkers in TypeScript. It allows developers to define types and validate data against those types at runtime. runtypes is designed to be simple and lightweight, making it easy to integrate into existing TypeScript projects. If you prefer a minimalistic approach to runtime type validation while still leveraging TypeScript's type system, runtypes is worth considering.

  • zod is a TypeScript-first schema declaration and validation library. It provides a simple and intuitive API for defining schemas and validating data, with a strong focus on TypeScript support. zod allows developers to create complex validation rules while maintaining type safety, making it a great choice for TypeScript applications. If you want a library that is easy to use and integrates well with TypeScript, zod is a strong contender.

To see how io-ts compares with joi, runtypes, and zod, check out the comparison: Comparing io-ts vs joi vs runtypes vs zod.

README for zod

Zod logo

Zod

TypeScript-first schema validation with static type inference
by @colinhacks


Zod CI status License npm discord server stars

Docs   •   Discord   •   𝕏   •   Bluesky


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Read the docs →



What is Zod?

Zod is a TypeScript-first validation library. Define a schema and parse some data with it. You'll get back a strongly typed, validated result.

import { z } from "zod/v4";

const User = z.object({
  name: z.string(),
});

// some untrusted data...
const input = {
  /* stuff */
};

// the parsed result is validated and type safe!
const data = User.parse(input);

// so you can use it with confidence :)
console.log(data.name);

Features

  • Zero external dependencies
  • Works in Node.js and all modern browsers
  • Tiny: 2kb core bundle (gzipped)
  • Immutable API: methods return a new instance
  • Concise interface
  • Works with TypeScript and plain JS
  • Built-in JSON Schema conversion
  • Extensive ecosystem

Installation

npm install zod

Basic usage

Before you can do anything else, you need to define a schema. For the purposes of this guide, we'll use a simple object schema.

import { z } from "zod/v4";

const Player = z.object({
  username: z.string(),
  xp: z.number(),
});

Parsing data

Given any Zod schema, use .parse to validate an input. If it's valid, Zod returns a strongly-typed deep clone of the input.

Player.parse({ username: "billie", xp: 100 });
// => returns { username: "billie", xp: 100 }

Note — If your schema uses certain asynchronous APIs like async refinements or transforms, you'll need to use the .parseAsync() method instead.

const schema = z.string().refine(async (val) => val.length <= 8);

await schema.parseAsync("hello");
// => "hello"

Handling errors

When validation fails, the .parse() method will throw a ZodError instance with granular information about the validation issues.

try {
  Player.parse({ username: 42, xp: "100" });
} catch (err) {
  if (error instanceof z.ZodError) {
    err.issues;
    /* [
      {
        expected: 'string',
        code: 'invalid_type',
        path: [ 'username' ],
        message: 'Invalid input: expected string'
      },
      {
        expected: 'number',
        code: 'invalid_type',
        path: [ 'xp' ],
        message: 'Invalid input: expected number'
      }
    ] */
  }
}

To avoid a try/catch block, you can use the .safeParse() method to get back a plain result object containing either the successfully parsed data or a ZodError. The result type is a discriminated union, so you can handle both cases conveniently.

const result = Player.safeParse({ username: 42, xp: "100" });
if (!result.success) {
  result.error; // ZodError instance
} else {
  result.data; // { username: string; xp: number }
}

Note — If your schema uses certain asynchronous APIs like async refinements or transforms, you'll need to use the .safeParseAsync() method instead.

const schema = z.string().refine(async (val) => val.length <= 8);

await schema.safeParseAsync("hello");
// => { success: true; data: "hello" }

Inferring types

Zod infers a static type from your schema definitions. You can extract this type with the z.infer<> utility and use it however you like.

const Player = z.object({
  username: z.string(),
  xp: z.number(),
});

// extract the inferred type
type Player = z.infer<typeof Player>;

// use it in your code
const player: Player = { username: "billie", xp: 100 };

In some cases, the input & output types of a schema can diverge. For instance, the .transform() API can convert the input from one type to another. In these cases, you can extract the input and output types independently:

const mySchema = z.string().transform((val) => val.length);

type MySchemaIn = z.input<typeof mySchema>;
// => string

type MySchemaOut = z.output<typeof mySchema>; // equivalent to z.infer<typeof mySchema>
// number
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