validator.js 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
A JavaScript library for checking and cleaning up strings, like emails, dates, and URLs.
Open source · MIT
A JavaScript/TypeScript library for defining schemas that validate and convert data at runtime.
The short answer
Choose validator.js if you need…
- JavaScript developers validating form or API input on Node.js
- Developers who need checks like isEmail or isDate without writing regular expressions themselves
- Projects that want to import only the individual validators they use
- Browser projects that load a standalone script or CDN file
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
| validator.js | Yup | |
|---|---|---|
| Type | Library | Library |
| Price | Free and open source | Free and open source |
| Licence | MIT | MIT |
| GitHub stars | 23.7k | 23.7k |
| Setup difficulty | Beginner | Beginner |
| How you get it | Install with a package manager | Install with a package manager |
| Main language | JavaScript | TypeScript |
| Last code update | 56 days ago | 7 days ago |
What each one is
validator.js
validator.js is a JavaScript library that provides many functions for checking whether a string matches a format, such as an email address, a date, or a credit card number, and for sanitizing strings. It is installed through npm and can be used on a server or in a browser. The README states it only works on strings, so other input must be converted to a string first.
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
validator.js
- JavaScript developers validating form or API input on Node.js
- Developers who need checks like isEmail or isDate without writing regular expressions themselves
- Projects that want to import only the individual validators they use
- Browser projects that load a standalone script or CDN file
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
validator.js
- Covers a wide range of common string checks in one package
- Lets you import only the validators you need to keep bundles smaller
- Works in both server-side Node.js code and in the browser
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
validator.js
- Anyone who needs validation of non-string data such as numbers or objects, since the README says non-string input causes an error
- Non-JavaScript projects, since the library is written for JavaScript and npm
- Non-developers, since it is a code library with no interface
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
validator.js
- Accepts only strings, so inputs must be converted before checking
- The README excerpt does not show how strict each check is, so results should be tested against your own rules
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
Frequently asked questions
What is the difference between validator.js and Yup?
validator.js: A JavaScript library for checking and cleaning up strings, like emails, dates, and URLs. Yup: A JavaScript/TypeScript library for defining schemas that validate and convert data at runtime. validator.js suits javascript developers validating form or api input on node.js, while Yup suits developers validating form or api input in javascript or typescript.
Are validator.js and Yup free?
validator.js: Free and open source. Yup: Free and open source.
Is validator.js or Yup more popular?
validator.js has more GitHub stars (23.7k) than Yup (23.7k). Popularity isn't the same as fit — check which one matches your use case above.
What are other alternatives to validator.js and Yup?
Other options people compare them with include Zod, VeeValidate, class-validator, Eureka, Ajv.
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.