Convert JSON to Protobuf online, free. JSON is the dominant data-interchange format for web APIs and config. Protobuf is a structured data format. JSON to Protobuf conversion parses your JSON against the ECMA-404 / RFC 8259 grammar (https://www.rfc-editor.org/rfc/rfc8259), builds an in-memory model of its keys, nested objects and arrays, then re-serializes it as valid Protobuf following the Protobuf format conventions. Processing runs in your browser in JavaScript with no upload or server round-trip — no size limit beyond your device's memory, so multi-megabyte documents convert in milliseconds and sensitive payloads never leave your machine. Typical uses include data interchange, configuration and tooling.
It maps the full structure of your JSON onto well-formed Protobuf, following the Protobuf format conventions. 100% free, no registration, and complete privacy — everything runs locally in your browser, so your data never touches a server.
Paste JSON and convert Protobuf immediately. Conversion runs client-side, so there is no upload wait and large documents stay fast.
Nested JSON objects, tables and arrays are mapped faithfully onto Protobuf.
Your JSON never leaves your device — everything is processed locally in JavaScript, with nothing logged or stored.
Unlimited conversions with no account, no quotas, and no watermark. Works on desktop and mobile.
A JSON document and its Protobuf equivalent:
JSON input:
{
"title": "Dune",
"pages": 412,
"available": true
}Output:
message Book {
string title = 1;
int32 pages = 2;
bool available = 3;
}Paste your JSON into the editor and press "Convert to Protobuf". The tool parses it against the ECMA-404 / RFC 8259 grammar, then re-serializes it as Protobuf following Protobuf format conventions — instantly and entirely in your browser. You can validate or format the JSON first to be sure it is clean.
JSON already uses objects, arrays and typed scalars, so mapping to Protobuf is close to one-to-one: objects become nested structures, arrays become lists, and numbers, booleans and null keep their types.
Numbers, booleans and null are preserved as native Protobuf types wherever Protobuf supports them, so standard documents convert losslessly and can be read back into the same structure.
JSON (JavaScript Object Notation) (JSON) — JSON is the dominant data-interchange format for web APIs and config. Protocol Buffers (.proto) (Protobuf) — Protobuf is a structured data format. This converter maps the structure of your JSON onto Protobuf so you can use it for data interchange.
Yes. Invalid JSON is flagged with a clear error before anything is converted. Common JSON problems to check are matched braces and brackets, double-quoted keys, and no trailing commas. Starting from clean input keeps the generated Protobuf accurate.
Yes. The entire JSON-to-Protobuf conversion runs locally in your browser in JavaScript — your JSON is never uploaded, logged or stored. That matters when the data is something like REST/GraphQL API payloads, which should not leave your machine.
The generated Protobuf is ready for data interchange, configuration and tooling. Copy or download it and drop it straight into your tooling.
Our tool makes it easy to convert JSON to Protocol Buffers (protobuf) schema! Just paste your JSON structure on the left, and the tool will automatically generate the corresponding protobuf schema on the right. You can then copy the schema and drop it right into your project. While the tool does a great job of making intelligent assumptions for the conversion, we recommend double-checking the output to ensure everything is perfect. This tool is here to save you time and simplify the process of working with protobufs.
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