Runtime validation with Zod
Types vanish at runtime, so anything crossing a boundary — a request body, a form, an environment variable, a third-party response — needs a real check.
Overview
One source of truth for a shape
Types vanish at runtime, so anything crossing a boundary — a request body, a form, an environment variable, a third-party response — needs a real check. A schema library gives you that check and the static type from a single declaration.
Inferring the type from the schema is what keeps the two aligned. Declaring an interface alongside a schema reintroduces exactly the drift you were trying to remove.
Validate environment variables at startup. Failing immediately with a clear message beats a null reference three hours into a deployment.
In this lesson you will:
- Define one schema and infer the type from it
- Validate untrusted input at the boundary
- Turn validation failures into useful messages
Resources
Notes are not saved yet — they clear when you leave this page.
Project references and monorepos
15m