Protobuf Decoder [2025]

This tool parses binary Protobuf data based on its fundamental encoding rules. It reads field tags (number + wire type) and interprets the following bytes according to the wire type (Varint, Fixed32/64, Length-Delimited).

Since it operates **without a .proto schema**, it cannot determine original field names or specific data types (e.g., `int32` vs. `uint64` for a Varint). Instead, it displays field numbers and provides the best-effort interpretation of the data (number, string, boolean guess, nested structure, or raw bytes). This is ideal for debugging, reverse-engineering, or quickly inspecting unknown Protobuf messages.

• Decode raw Protobuf binary data into JSON
• Accepts Base64, Hex text, or file upload
• Identifies field numbers & wire types
• Interprets strings & nested messages
• Displays binary data as Hex
• Handles basic nested structures
• Supports large numbers (via BigInt)
• Clear error messages for invalid data
• Client-side processing for privacy
• Includes common examples
• Copy output to clipboard
• Responsive design

Protobuf uses different wire types to efficiently encode various data types:

• Varint (Type 0): Integers (`int32`, `int64`, `bool`, `enum`, etc.). Variable byte length.
• 64-bit Fixed (Type 1): Fixed 8-byte numbers (`fixed64`, `double`).
• Length-Delimited (Type 2): Variable-length data (`string`, `bytes`, nested messages). Length prefix + data.
• 32-bit Fixed (Type 5): Fixed 4-byte numbers (`fixed32`, `float`).
• Start/End Group (Types 3, 4): Deprecated structure markers.