Protobuf Decoder
Decode a Protocol Buffers message from hex or base64 without its .proto schema, showing each field number, wire type and the possible readings of its value.
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Input
Decode Protocol Buffers without a schema
Output
25 bytes, 7 fields
| Field | Type | Value |
|---|---|---|
| 1 | varint | 150 (zigzag 75) |
| 2 | bytes | "testing" |
| 3 | message | 6 bytes (decoded below) |
| 3.1 | message | 4 bytes (decoded below) |
| 3.1.1 | varint | 1 (zigzag -1) |
| 3.1.2 | varint | 2 (zigzag 1) |
| 4 | i32 | 1065353216 / float 1 |
Without the .proto file only the wire format is known: each field's number and wire type. A varint could be an int, a bool or an enum (shown with its zigzag reading for sint fields); a length-delimited field could be a string, bytes or a nested message, so all plausible readings are shown. protoc --decode_raw gives the same view on the command line. For gRPC, strip the 5-byte frame header first.
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About this tool
Method, assumptions, practical next steps, and limits.
What the wire format tells you
Protocol Buffers encode field numbers and wire types, not names or exact types, so without the schema some ambiguity remains: a varint may be an int, a bool or an enum, and a length-delimited field may be a string, bytes or a nested message. The encoding guide explains each wire type. protoc --decode_raw gives the same view on the command line.
gRPC payloads
A gRPC message on the wire starts with a 5-byte header: one compression flag byte and a 4-byte length. Remove it before decoding the rest as a protobuf message.
