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Free online JSON to Protobuf converter. Instantly generate Protocol Buffers message definitions from JSON data.
Automatically convert camelCase to snake_case, following Protobuf style guidelines.
Enter JSON to generate the corresponding .proto file structure.
When using Protobuf for data exchange in development, manually writing .proto files can be error-prone and time-consuming. This tool automatically converts JSON data into corresponding Protobuf message definitions. It infers Protobuf types such as string, int32, double, and bool based on JSON field values, supports nested objects and arrays, and quickly generates usable Proto message structures.
Example JSON Input:
{
"name": "Alice",
"age": 25,
"active": true,
"scores": [98, 87],
"address": {
"street": "Main St",
"city": "NY"
}
}
Example Protobuf Output:
syntax = "proto3";
message AutoGenerate {
string name = 1;
int32 age = 2;
bool active = 3;
repeated int32 scores = 4;
Address address = 5;
}
message Address {
string street = 1;
string city = 2;
}
The input JSON must be a valid object or array format. Null values will be ignored or prompt an adjustment. Automatically generated field numbers increment sequentially based on the JSON keys; if you need fixed numbers, please modify them manually. This tool processes data entirely locally in your browser and does not send content to any servers, so you can use it with peace of mind.
The generated .proto file serves as a great foundation, but we still recommend verifying that the field types meet your actual requirements (e.g., adjusting int32 to sint32, fixed64, etc.). For complex business models, you can add advanced structures like enums and oneof after generating the message framework. Common conversion rules: If JSON array elements are of the same type, a repeated field is generated; if array element types are inconsistent, the tool may attempt to generate a oneof or throw an error. In such cases, it is advisable to standardize your data format first.

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