Protobuf decoder

Protocol Buffers (protobuf) is Google's compact binary serialization format, used by gRPC, many Google APIs, Kubernetes internals and mobile apps. Because protobuf messages are binary and field names are not included, captured payloads are unreadable without the .proto schema. This decoder parses the wire format directly, showing field numbers, wire types and values so you can debug messages even when you do not have the schema.

How to use it

1. Paste the message bytes as hex.
2. Review the decoded field list.
3. Match field numbers to your schema if you have it.

How the wire format works

A message is a sequence of key-value pairs. Each key is a varint containing (field_number << 3) | wire_type. Wire types are:

• 0 VARINT: int32, int64, uint, bool, enum.
• 1 I64: fixed64, sfixed64, double.
• 2 LEN: strings, bytes, nested messages and packed repeated fields, preceded by a length.
• 5 I32: fixed32, sfixed32, float.

Example

Hex 08 96 01 12 04 74 65 73 74 decodes as:

• 08: field 1, varint; 96 01 = 150.
• 12: field 2, length-delimited; 04 = 4 bytes; 74 65 73 74 = test.

Limits of schemaless decoding

• Field names are unknown; only numbers are shown.
• A length-delimited field could be a string, raw bytes or a nested message; the decoder guesses.
• Varints could be signed with zigzag encoding (sint32) or plain; values may need reinterpretation.
• gRPC frames add a 5-byte prefix (compression flag and length) before the protobuf message; remove it first.