JSON to Zod
Writing a Zod schema by hand for an API response you already have is transcription, not design. Paste one or more samples and this infers the field types, marks the keys that are missing from some samples as optional, and emits a schema plus the matching inferred TypeScript type.
A single object cannot reveal which keys are optional. Paste an array of several samples to detect them.
Technical Guide & Mechanics
Automated Zod Schema Synthesis from Runtime Payloads
Zod has become the gold standard for runtime data validation in the TypeScript ecosystem. However, manually transcribing nested JSON responses into Zod schemas is both error-prone and tedious. The challenge compounds when dealing with production payloads where certain fields only appear conditionally or contain null values depending on object lifecycle states.
Our inference engine parses one or multiple sample objects simultaneously. When evaluating multiple samples, it computes the mathematical union of all discovered object shapes. If a property is present in sample A but missing in sample B, the engine automatically tags it with .optional(). If a property contains a concrete type in one sample and null in another, it tags it with .nullable(). This eliminates the common mistake of conflating absence (undefined) with nullability (null).
The generated code includes both the executable Zod schema definition and the exported TypeScript type inferred via z.infer<typeof Schema>. This guarantees complete end-to-end type safety across API boundaries, server actions, and frontend forms.
how to use it
- 01Paste a JSON object, an array of samples, or NDJSON.
- 02Check the inferred optional and nullable flags.
- 03Copy the generated schema into your project.
questions
- Why do I need more than one sample?
- A single object cannot tell you whether a missing key is optional or simply absent that once. Given several samples, a key present in some and not others is inferred as optional.
- How are nulls handled?
- A field that is null in a sample and typed in another becomes nullable rather than losing its type.
- Does it support array of objects?
- Yes. When an array of sample objects is provided, all entries are merged to establish the canonical schema union.
- Can I infer TypeScript types from the generated Zod schema?
- Yes, the generated output automatically includes export type MySchema = z.infer<typeof MySchema> for seamless static typing.