FreeDev Tools

JSON to Protobuf

Generate proto3 message definitions from JSON — field numbers, repeated fields, and nested messages.

Runs locally in your browser. Your input is not uploaded.

How to Use

  1. 1

    Paste sample JSON

    Paste one representative object of the message you want to model.

  2. 2

    Review types and numbering

    Check int64 vs double inference and rename Root to your message name.

  3. 3

    Copy into a .proto file

    Save the output and compile with protoc for your target language.

Frequently Asked Questions

proto3 message definitions with fields, sequential field numbers, repeated markers for arrays, and nested message types — inferred from your JSON sample.

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