Protobuf ↔ JSON Converter

Decode a hex/base64 protobuf message against a .proto schema, or preview the wire bytes for a JSON payload.

Mode Encoding

.proto schema Message name (optional — defaults to first) Encoded message

Field-tag map (from schema)Output

Paste a schema and encoded message to decode.

About this tool

Paste a proto3 schema plus a hex or base64 encoded message to decode it into JSON; or paste JSON to preview the protobuf wire bytes. The decoder is a hand-rolled wire-format parser that handles varint, fixed32, fixed64 and length-delimited fields, scalars (int32/64, uint32/64, sint32/64, fixed32/64, sfixed32/64, bool, float, double, string, bytes), enums (rendered as numeric tag), nested messages and repeated fields. Limitations: oneof, maps, packed repeated fields, groups and well-known types are not modelled; unknown fields are surfaced under _unknown_<tag>.