class-validator vs Yup
Which should you use? A side-by-side look at what each one does, who it suits, what it costs, how hard it is to set up, and where each falls short.
Open source · MIT
Validates class properties using TypeScript decorators, for browser and Node.js.
Open source · MIT
A JavaScript/TypeScript library for defining schemas that validate and convert data at runtime.
The short answer
Choose class-validator if you need…
- TypeScript developers validating request bodies or form data in Node.js or the browser
- Projects that already model data as classes and want validation rules next to the fields
- Teams building APIs who want to return structured validation errors to clients
Choose Yup if you need…
- Developers validating form or API input in JavaScript or TypeScript
- Teams that want TypeScript types inferred from a validation schema
- Projects that need async validation, such as checking against a server
- Developers who want to extend schemas with their own custom methods
Side-by-side
| class-validator | Yup | |
|---|---|---|
| Type | Library | Library |
| Price | Free and open source | Free and open source |
| Licence | MIT | MIT |
| GitHub stars | 11.9k | 23.7k |
| Setup difficulty | Beginner | Beginner |
| How you get it | Install with a package manager | Install with a package manager |
| Main language | TypeScript | TypeScript |
| Last code update | 8 months ago | 6 days ago |
What each one is
class-validator
class-validator lets you attach validation rules to the properties of a class using decorators, such as checking that a string is an email or a number is within a range. You then call validate on an object and get back a list of errors for anything that fails. It also supports non-decorator schemas, and it uses validator.js internally to run the checks.
Yup
Yup lets you describe the expected shape of a value, such as a user object with a name, age, and email, using chained method calls. You can then check incoming data against that schema, or convert ('cast') it into the correct types. It is commonly used to check form input or API data before using it.
Best for
class-validator
- TypeScript developers validating request bodies or form data in Node.js or the browser
- Projects that already model data as classes and want validation rules next to the fields
- Teams building APIs who want to return structured validation errors to clients
Yup
- Developers validating form or API input in JavaScript or TypeScript
- Teams that want TypeScript types inferred from a validation schema
- Projects that need async validation, such as checking against a server
- Developers who want to extend schemas with their own custom methods
Strengths
class-validator
- Rules are declared next to the fields they check, which keeps models readable
- Returns structured ValidationError objects with property names and constraint messages
- Works in both browser and Node.js environments according to the README
Yup
- Concise chained syntax that the README describes as expressive enough for complex, interdependent validations
- Strong TypeScript support, including inferring static types from schemas
- Clear error details and support for custom error messages and localization
Not ideal for
class-validator
- Projects that do not use TypeScript or decorators, since the main API depends on them (the README also offers a non-decorator option, which is less covered in the excerpt)
- Users who need a full schema language with type inference from one definition, as the README does not compare against such tools
Yup
- Projects that do not use JavaScript or TypeScript, since the library is written for that ecosystem
- Users who need a non-developer tool with a visual interface
- Projects on the pre-v1 API, since the README points to a separate pre-v1 branch for those docs
Trade-offs
class-validator
- The README says forbidUnknownValues defaults to true and advises keeping it; turning it off lets unknown objects pass validation
- Requires npm 6 or later so the dependency tree is flattened correctly
- The README excerpt is truncated, so details of many decorators and advanced features were not reviewed
Yup
- The README is truncated, so this summary covers only the first part of the API reference
- Its full feature set and edge cases are documented elsewhere and were not visible here
- Pre-v1 users must use a different documentation branch
Getting started
class-validator
Install the package
npm install class-validator --saveFrequently asked questions
What is the difference between class-validator and Yup?
class-validator: Validates class properties using TypeScript decorators, for browser and Node.js. Yup: A JavaScript/TypeScript library for defining schemas that validate and convert data at runtime. class-validator suits typescript developers validating request bodies or form data in node.js or the browser, while Yup suits developers validating form or api input in javascript or typescript.
Are class-validator and Yup free?
class-validator: Free and open source. Yup: Free and open source.
Is class-validator or Yup more popular?
Yup has more GitHub stars (23.7k) than class-validator (11.9k). Popularity isn't the same as fit — check which one matches your use case above.
What are other alternatives to class-validator and Yup?
Other options people compare them with include Zod, Ajv, validator.js, VeeValidate.
Keep comparing
Built from our catalogue entries for both products: open-source details come from each project's README (AI-assisted, refreshed weekly) and GitHub data; AI-tool details are editorial. Spotted something wrong? Let us know from either product's page.