What does the JSON to Zod generator do?
It takes a sample JSON payload and generates a Zod schema that validates it: objects become z.object(), arrays become z.array() with element types inferred from the actual items (unions when they're mixed), integers become z.number().int(), and nested objects are hoisted into named sub-schemas so the output stays readable. Each schema ships with an inferred TypeScript type via z.infer, so you get runtime validation and static types from one source of truth.
Generation runs entirely in your browser — the payload you paste is never uploaded or logged, so real API responses with production data are safe to use as samples.
When to use it
Reach for it whenever data crosses a trust boundary: an external API response, a webhook payload, the JSON column you just read from the database, or user-supplied config. TypeScript types are erased at runtime — a fetch response typed as User is a polite fiction until something validates it. Writing that Zod schema by hand for a deeply nested payload is tedious and error-prone; generating it from a real sample takes seconds and catches the fields you'd forget.
The generated schema is a starting point, deliberately strict and literal. Expect to refine it: mark fields that aren't always present as .optional(), widen z.null() to z.string().nullable() where a value merely happened to be null in your sample, and add constraints like .email() or .min() where they encode real rules.
Example
Paste {"id": 1, "name": "Alice", "active": true, "address": {"city": "Oslo"}} with root name User and you get an AddressSchema, a UserSchema referencing it, and exported User / Address types inferred from them. Calling UserSchema.parse(data) then rejects any payload where the API drifted from the shape you sampled — usually the exact moment you want a loud failure instead of a silent undefined. Use "Copy link to this result" to share a permalink that restores your sample and root name, and if you only need static types without runtime validation, there's a companion JSON to TypeScript tool.
How to use the JSON to Zod Schema Generator tool
- 1
Paste a sample payload
A real API response works best — the more representative the sample, the better the inferred schema.
- 2
Name the root schema
The name (e.g. User) becomes the exported schema const and its inferred TypeScript type.
- 3
Generate and refine
Add .optional(), .nullable(), and constraints like .email() where your sample doesn't tell the whole story.
- 4
Copy or share
Copy the schema into your codebase, or copy a permalink that restores your exact input for a teammate.
Frequently asked questions
Is my JSON uploaded anywhere?
No. Parsing and schema generation run entirely in your browser, so production payloads are safe to paste. Permalinks encode the sample in the URL fragment, which is never sent to a server.
Why are null fields typed as z.null()?
The generator only sees your sample, and in the sample the value is null. If the field can also hold a value, widen it yourself — e.g. z.string().nullable(). The same applies to fields that are sometimes absent: add .optional(), since a single sample can't reveal optionality.
How are arrays with mixed element types handled?
Element schemas are inferred per item and deduplicated: uniform arrays become z.array(z.string()) and mixed ones become a union like z.array(z.union([z.string(), z.number()])). Empty arrays come out as z.array(z.unknown()) because there's nothing to infer from.
What if I just want TypeScript types, not validation?
Use the companion JSON to TypeScript tool — it emits plain interfaces with zero runtime cost. Choose Zod when data crosses a trust boundary (APIs, webhooks, user input) and you want parsing that fails loudly at runtime, then derive the types with z.infer.
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