Proto to JSON Converter

Generate sample JSON from a Protobuf (.proto) schema. Runs locally in your browser.

Protobuf Schema

JSON Output

{
  "orderId": "orderId-1",
  "customer": {
    "name": "name-1",
    "email": "[email protected]"
  },
  "items": [
    {
      "sku": "sku-1",
      "quantity": 1,
      "unitPriceCents": "1"
    }
  ],
  "status": "ORDER_STATUS_PENDING"
}

The Kafka IDE

Mock and produce Protobuf messages in Kafma

Kafma is a desktop app for Kafka. Generate sample JSON from your Schema Registry with registered references resolved, then edit, validate, and produce Protobuf messages to a topic.

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Kafma desktop app generating sample JSON from the OrderConfirmed Protobuf schema in the Schema Registry Mock tab
Kafka Schema Explorer

Protobuf to JSON FAQ

Why did user_id become userId in Protobuf JSON?
The ProtoJSON mapping uses lowerCamelCase field names by default. A snake_case field like user_id becomes userId unless the field sets json_name. See the Protobuf JSON mapping
Why are int64 values quoted in Protobuf JSON?
64-bit integer fields are emitted as strings to preserve precision. 32-bit integer fields remain JSON numbers. See the Protobuf JSON mapping
Why is a Protobuf import missing or a type unknown?
This tool does not fetch external files or Schema Registry subjects. Paste the missing definitions into the editor and remove their import lines; type names and packages must match. Built-in Google well-known types are supported.
Why are nested fields missing from the sample JSON?
Check the selected message type above the output. Nested user messages stop expanding at depth 4, and each oneof includes only one branch. Copy the JSON into your editor to fill in the nested values your test needs.
Can I send this JSON directly as a Protobuf Kafka message?
The JSON is a sample editing input, not a binary Protobuf payload. Sending Protobuf requires the matching schema, message type, and serializer. In Kafma, select the schema in Kafka Console, generate or edit a payload, then produce it.
Can I decode binary Protobuf to JSON?
No. This page generates sample JSON from a .proto schema. It does not decode binary Protobuf payloads. To read live Kafka messages, use Kafka Console.
Is my input uploaded?
No. Conversion runs in your browser. Your input and generated output are not uploaded.
Can I generate a .proto schema from sample JSON?
Use the JSON to Proto converter to infer a .proto schema from sample JSON.