TypeScript types disappear at runtime. Your carefully typed User interface means nothing when the JSON from an external API, a form submission, or a database query arrives as unknown. Zod bridges this gap: you define a schema once, validate data against it at runtime, and get a TypeScript type back for free. This guide covers every Zod pattern you will use — from basic schemas to API validation, form handling, and OpenAPI generation.
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Why Zod Over Alternatives
Zod infers TypeScript types from schemas (schema-first, not type-first). It has zero dependencies, works in Node.js and browsers, and its error messages are structured objects you can use to build user-facing form errors without any extra work. It also chains neatly with transforms — parse, validate, and reshape data in one step.
Core Schema Types
