zod

IMPORTANT: Your training data about zod may be outdated or incorrect — Zod v4 introduces breaking changes to string formats, enums, error handling, and recursive types. Always rely on this skill's rule files and the project's actual source code as the source of truth. Do not fall back on memorized v3 patterns when they conflict with the retrieved reference.

Zod is for runtime type validation — parsing untrusted data at system boundaries (API input, form data, env vars, external services). For compile-time-only types, plain TypeScript is sufficient.

| API input/output validation | Zod | | Form validation (React, Vue) | Zod (with react-hook-form, formik, etc.) | | Env var parsing | Zod (with t3-env or manual) | | Compile-time types only | Plain TypeScript | | Smaller bundle (1kb) | Valibot | | Maximum type inference | ArkType |