zod vs yup

validation

zod

yup

Zod and Yup are both schema validation libraries for JavaScript and TypeScript that enable runtime data validation for forms, APIs, and configuration objects. Zod is a TypeScript-first library designed with modern type inference capabilities, allowing developers to derive static types directly from runtime schemas. Yup is a mature, established validation library with a chainable API that emphasizes flexibility and readability, widely adopted in form libraries like Formik and React Hook Form.

This comparison matters because choosing between them significantly impacts your development workflow, type safety guarantees, and bundle size. Zod targets teams building TypeScript applications who want compile-time type safety synchronized with runtime validation, while Yup serves developers—particularly those working with JavaScript or mixed codebases—who need expressive, customizable validation with extensive ecosystem integration. Both handle validation effectively, but their philosophies and optimal use cases diverge substantially.

Head-to-Head

TypeScript Integration→ zod wins

zod

Native TypeScript-first design with automatic type inference via z.infer<typeof schema>. Types are guaranteed to match runtime validation, eliminating manual typing and drift between schemas and types. Supports complex type operations like unions, intersections, and discriminated unions with full IDE autocomplete.

yup

Provides TypeScript definitions but requires manual type annotations. Type inference is basic and doesn't automatically derive from schemas, creating potential mismatches between runtime validation and compile-time types. Developers must maintain separate type definitions or use helper utilities.

API Design & Expressiveness→ yup wins

zod

Concise, immutable, object-oriented API with strong composability through methods like union(), intersection(), and refine(). Parse-or-throw pattern with safeParse() for error handling. Less verbose but requires familiarity with its specific patterns for complex conditional logic.

yup

Declarative chaining API with intuitive methods like .when() for conditional validation, .test() for custom validators, and context-aware validation. More expressive for complex business rules and offers inline error customization. The API reads naturally but can become verbose in large schemas.

Runtime Performance→ zod wins

zod

Optimized parse-or-throw execution model with minimal overhead. TypeScript optimizations reduce runtime checks. Benchmarks show 20-40% faster validation on complex nested schemas compared to Yup, especially with large data sets.

yup

Performs well on simple to medium validations but shows performance degradation on deeply nested objects and large arrays due to chaining overhead and context evaluation. Async validation adds latency but provides flexibility for database checks.

Bundle Size→ zod wins

zod

Approximately 12-14kb minified + gzipped with excellent tree-shaking support. Modular design allows bundlers to eliminate unused validators effectively. Footprint remains consistent even with complex schemas due to code reuse.

yup

Approximately 14-17kb minified + gzipped, growing larger with extensive custom validators and chaining. Less aggressive tree-shaking due to prototype-based methods. The difference becomes notable in bundle-sensitive applications.

Ecosystem & Integrations→ yup wins

zod

Growing ecosystem with tRPC, Next.js, and modern frameworks. Smaller community but highly active among TypeScript developers. Fewer third-party integrations and examples compared to Yup, requiring more custom implementation for established patterns.

yup

Mature ecosystem with extensive documentation, tutorials, and examples. Deep integrations with Formik, React Hook Form, and major form libraries. Larger community means more Stack Overflow answers, plugins, and battle-tested patterns for common scenarios.

Validation Featurestie

zod

Supports function input/output validation, transformers (transform()), and refinements (refine(), superRefine()) for complex business logic. Primitives, objects, arrays, tuples, discriminated unions, and recursive types. No built-in async validation but can be composed with promises.

yup

Built-in async validation for database lookups and external checks. Features like cast() for type coercion, abortEarly for performance, strict mode, and context-aware tests. More out-of-the-box validators for common patterns like URLs, UUIDs, and dates with localization.

Verdict

Choose Zod if you're building TypeScript applications where type safety is non-negotiable. Its automatic type inference eliminates an entire class of bugs by ensuring your runtime validation and compile-time types never drift apart. The performance advantages, smaller bundle size, and composability make it the superior choice for greenfield TypeScript projects, API validation layers, or any codebase where developers expect tight integration between validation and the type system. Zod's learning curve is steeper for developers unfamiliar with its patterns, but the productivity gains in TypeScript environments justify the investment.

Choose Yup if you're working in JavaScript-heavy codebases, maintaining legacy applications, or building form-intensive UIs with libraries like Formik. Its expressive API, mature ecosystem, and extensive documentation reduce implementation time for common validation patterns. The built-in async validation and cast() functionality handle real-world scenarios that would require custom solutions in Zod. Yup's flexibility with custom error messages and context-aware validation makes it ideal when business requirements demand nuanced validation logic that must be easily understood by diverse development teams.

When to Use Each

If you are building a tRPC API with end-to-end type safety → use Zod because it seamlessly shares schemas between client and server with automatic TypeScript inference, eliminating redundant type definitions.

If you are implementing complex multi-step forms in a React application with Formik → use Yup because its mature integration, async validation support, and expressive conditional logic (.when()) handle form complexity with less boilerplate.

If you are validating configuration objects or environment variables in a Node.js TypeScript backend → use Zod because the parse-or-throw pattern catches misconfigurations at startup and automatically types your config object throughout the application.

If you are maintaining a JavaScript codebase with mixed JS/TS files where gradual TypeScript adoption is the goal → use Yup because it works excellently without TypeScript, provides value immediately, and doesn't require rewriting validation logic when eventually adding types.

Learn More

zod →yup →