Protobuf to JSON Schema

The Protobuf to JSON Schema is a free online tool that convert proto3 definitions to json schema, typescript interfaces, and sample json. supports messages, enums, nested types, oneof, map, repeated.. It runs entirely in your browser with no installation or sign-up needed.

Proto3: messages, enums, nested messages, repeated, optional, oneof, map fields, all scalar types.

Three: JSON Schema (Draft-07 with $ref), TypeScript interfaces, and sample JSON with placeholder values.

Mapped to string in both JSON Schema and TypeScript, following the standard protobuf JSON mapping convention for 64-bit integers.

Yes, the Protobuf to JSON Schema is 100% free with no registration, no hidden fees, and no usage limits. All processing happens locally in your browser, ensuring complete privacy.

Absolutely. The Protobuf to JSON Schema processes everything client-side in your browser. No data is uploaded to or stored on any server. Your content remains private on your device at all times.

Yes, the Protobuf to JSON Schema is fully responsive and works on smartphones and tablets. You can use it on any device with a modern web browser -- no app download required.

No account or registration is needed. Simply open the Protobuf to JSON Schema in your browser and start using it immediately. There are no sign-up walls or usage restrictions.

The Protobuf to JSON Schema supports a wide range of popular formats and languages. Check the tool interface for the full list of supported options.

Simply enter your input in the provided field, adjust any settings to your preference, and the tool will process it instantly. You can then copy the result to your clipboard or download it.

A .proto file is the source definition for Protocol Buffers: it declares messages, fields, types, and field numbers used to serialize compact binary data for gRPC and high-throughput APIs. A JSON Schema describes the shape of a JSON document so validators can check that incoming or outgoing payloads have the right fields and types. They serve the same idea -- a data contract -- but in different worlds: protobuf governs binary wire format, while JSON Schema governs human-readable JSON used in web APIs, configs, and docs. Converting one to the other lets you validate JSON against the same structure your services already enforce in binary. This tool reads a proto3 definition and emits a Draft-07 JSON Schema, using $ref pointers into a shared definitions block, so you can drop it straight into a validator without rewriting field names by hand.

Sixty-four-bit integer types -- int64, uint64, sint64, fixed64, and sfixed64 -- are represented as strings rather than numbers in both the JSON Schema and the sample JSON. This is not a quirk of the converter; it follows the official Protobuf JSON mapping. JavaScript's number type is a double-precision float that can only safely represent integers up to 2^53, so a true 64-bit value could silently lose precision if parsed as a number. Encoding it as a string preserves every digit and round-trips cleanly across languages. Thirty-two-bit integers like int32 and uint32 stay as plain numbers, since they fit comfortably. Knowing this prevents validation surprises when a backend sends a large ID or timestamp. Paste your schema here and the tool applies the string-versus-number rule automatically for every numeric field.

Each protobuf construct maps to its natural JSON equivalent. A repeated field becomes a JSON array and a TypeScript array type, since it holds zero or more values. A map<key, value> field is rendered as a JSON object using additionalProperties to type the values, because protobuf maps are key-value collections. A oneof block emits every member field, and the JSON Schema records that the options are mutually exclusive, so only one can be set at a time. Optional fields become non-required in the schema and gain a ? in the TypeScript interface, while scalar and nested message types resolve through $ref pointers. This means complex real-world schemas translate faithfully rather than being flattened or dropped. Click Sample .proto to load an example that includes a repeated field, a map, and a oneof, then compare the tabs to see exactly how each is handled.

The sample JSON tab builds a complete example object by filling every field with a representative placeholder so you can see the message shape immediately. A string becomes "example", a double becomes 3.14, integer fields get stand-in numbers, and a bytes field shows a short base64-encoded string like "dGVzdA==" because bytes are typed as base64 strings in JSON. Repeated fields appear as arrays, maps as objects, and nested messages are expanded inline. These are not real data -- they are typed stand-ins meant to seed a fixture, a Postman request body, or a mock API response without typing a realistic payload by hand. Because the values match each field's type, the example will pass against the JSON Schema the tool generates from the same proto. Paste your schema and open the Sample JSON tab to copy or download a ready-to-edit example.

Yes. Alongside the JSON Schema, the converter produces ready-to-use TypeScript: one interface per message and a real enum per protobuf enum, so the output drops straight into a project and gives you compile-time typing. Field types follow the protobuf JSON mapping -- strings, numbers, booleans, arrays for repeated fields, and ? markers on optional fields. Sixty-four-bit integers are typed as string to avoid precision loss, and bytes fields are typed as base64 strings. Inline comments in your .proto carry through as descriptions, keeping the generated types documented. This keeps a frontend in sync with the backend's source of truth without hand-copying field names every time the schema changes, which is where typos and drift usually creep in. Paste your proto3 definition, switch to the TypeScript tab, then copy the result or download it as types.ts.