These aren't really competitors — they're two different answers to "how do I describe the shape of this data," aimed at different consumers. JSON Schema is a specification: a plain JSON document that describes a shape, and any language with a conforming validator (Python's jsonschema, Go's gojsonschema, JavaScript's ajv) can check data against it. Zod is a TypeScript library: you write a schema in TypeScript code, and it gives you both a runtime validator and a static type (z.infer<typeof Schema>) from that one definition.
// JSON Schema — a document, not code
{ "type": "object", "properties": { "id": { "type": "number" } }, "required": ["id"] }
// Zod — TypeScript code
import { z } from 'zod'
const Schema = z.object({ id: z.number() })
type Shape = z.infer<typeof Schema> // TypeScript type, derived automaticallyPick JSON Schema when the schema needs to leave TypeScript
If the consumer of your schema is an OpenAPI spec, a non-TypeScript backend, a form-generation library, or anything that isn't your own TS codebase, JSON Schema is the right layer — it's language-neutral by design, and Zod schemas don't serialize into it without a conversion step. If you're validating data at a boundary that isn't exclusively TypeScript-to-TypeScript, reach for JSON Schema first.
Pick Zod when you want one definition, not two
Using JSON Schema inside a TypeScript project usually means writing (or generating) the schema, and then separately writing or generating a matching TypeScript type — two artifacts that can drift out of sync if one gets edited and the other doesn't. Zod collapses that into one definition: the validator and the type come from the same source, so they can't disagree with each other. The cost is that the schema only exists as TypeScript code — nothing outside a JS/TS runtime can read it directly.
Where this repo's tools land on that split
The JSON Schema Generator produces a draft-07 document — useful if you need a portable schema, or you're validating data outside a TypeScript codebase. Living Types generates a Zod schema directly (plus the matching TypeScript type) from the same underlying multi-sample inference, which is the better fit if everything downstream is already TypeScript and you don't want to hand-maintain a second type definition next to the schema.
Neither one gives you drift detection by itself
A JSON Schema document or a Zod schema both describe a shape at the moment you wrote them — neither one tells you, on its own, that a live API's actual response has since diverged from what you generated against. That's a separate concern from validation: it requires keeping the schema (or a snapshot of it) around and comparing a fresh sample against it later, which is what a snapshot-diffing step adds on top of either format.