Protobuf to JSON Converter

Example: Protobuf input and real JSON output

The output below was generated by the same conversion code the converter uses, run on this sample when the page was built.

user {
  id: 42
  email: "dev@example.com"
  active: true
  roles: "admin"
  roles: "billing"
  profile {
    display_name: "Dev Ops"
    locale: "en-SE"
  }
}

{
  "user": {
    "id": 42,
    "email": "dev@example.com",
    "active": true,
    "roles": [
      "admin",
      "billing"
    ],
    "profile": {
      "display_name": "Dev Ops",
      "locale": "en-SE"
    }
  }
}

JSON output is 37% larger than the Protobuf input. The same data is 140 characters as minified JSON and 218 as pretty-printed JSON. Sizes are character counts, not tokens: token counts depend on the model's tokenizer (see the tokenizer comparison).

Protobuf to JSON: what changes

• Repeated roles fields are collected into a JSON array. Without the .proto schema, field numbers, enums, and int64 versus int32 cannot be recovered; only the text values are available.
• Reading Protobuf: Input is Protobuf text format (the readable form used in .textproto files and debug output), not the binary wire format. Repeated fields are collected into arrays; no .proto schema is read, so types are inferred from the values.
• Writing JSON: Output is pretty-printed with your chosen indentation. JSON is the safest target when the data goes into code, an API, or another tool.

Why Convert Protobuf to JSON?

Use JSON when you need maximum compatibility with other systems, APIs, or programming languages. It's the de facto standard for web APIs and data exchange.