Question 1

What is Protocol Buffers (protobuf)?

Accepted Answer

Protocol Buffers (protobuf) is a language-neutral, platform-neutral, extensible mechanism developed by Google for serializing structured data. It is smaller, faster, and simpler than XML or JSON. You define how you want your data to be structured once in a .proto file, and you can use generated source code to easily write and read your structured data to and from a variety of data streams using a variety of languages.

Question 2

What is raw / schema-less protobuf decoding?

Accepted Answer

Raw decoding reads protobuf binary data at the wire-format level without needing a .proto schema file. Each field is identified by its field number and wire type (Varint, 64-bit, Length-delimited, 32-bit). This is useful for inspecting unknown protobuf payloads, debugging gRPC traffic, or reverse-engineering binary data. The decoded output shows field numbers and values, but field names are only available with a .proto schema.

Question 3

What input formats are supported?

Accepted Answer

The decoder accepts protobuf data encoded as Base64 (standard RFC 4648 encoding, as commonly seen in gRPC-Web, REST APIs returning binary data, and debugging tools) or Hex (hexadecimal string, useful when inspecting raw binary dumps or network captures). Whitespace is ignored in both formats.

Question 4

What do the wire types mean?

Accepted Answer

Protobuf wire types describe how a field's value is encoded in the binary format. Wire type 0 (Varint) is used for int32, int64, uint32, uint64, sint32, sint64, bool, and enum fields. Wire type 1 (64-bit) is used for fixed64, sfixed64, and double fields. Wire type 2 (Length-delimited) is used for string, bytes, embedded messages, and repeated fields. Wire type 5 (32-bit) is used for fixed32, sfixed32, and float fields. Wire types 3 and 4 (start/end group) are deprecated.

Field #	Wire Type	Value
1	Varint(0)	150
2	Length-delimited(2)	testing

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Protobuf Decoder / Encoder

Base64 encoded protobuf

Decoded fields (2)