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JSON to Protobuf (Proto3) — Generate .proto Message Definitions

Paste JSON to generate Protocol Buffers (Proto3) message definitions — field types inferred and numbered correctly — ready to drop into a .proto file. For JSON with many nested objects that each deserve their own separate named message, JSON to Protobuf Schema offers more structured message splitting.

How to use JSON to Protobuf (Proto3)

1. Paste your JSON.
2. Review the generated .proto message definition.
3. Copy it into your .proto file.

Frequently asked questions

Why do Protobuf fields need numbers?

Field numbers, not names, are what Protobuf uses on the wire for binary encoding — they must be unique within a message and, once used in a released schema, generally should not be reused for a different field.

How is this different from JSON to Protobuf Schema?

Both generate Proto3 definitions from JSON; this one is the quick single-message version, while JSON to Protobuf Schema focuses on splitting deeply nested JSON into multiple clearly named messages.

Does it infer repeated fields for JSON arrays?

Yes — array fields generate the correct repeated field syntax.

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