Decode MessagePack data

Decode MessagePack bytes into nested values and identify each binary type prefix.

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ToolMessagePack Viewer

Input

Output

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How it works

The first byte selects a compact integer, string, array, map, float, binary, or extension format, and length bytes determine the payload size. Supported arrays and maps are decoded recursively until their declared contents end.

Hex is used because MessagePack is binary.
Recursive decoding follows the format’s explicit lengths.

Worked example

Decode fixmap with string key-value pair

Decode a base64-encoded MessagePack map containing {"name":"Alice"}

Input

											gaRuYW1lpUFsaWNl

Output

												Hex: 81 a4 6e 61 6d 65 a5 41 6c 69 63 65
Byte length: 12
Format: Fixmap (1 elements)

DECODED
Name: Alice

When to use this

Game packets, service caches, and protocol captures use compact MessagePack payloads.

Edge cases

A declared string or map length beyond remaining bytes is truncated and fails.
Extension records retain application-defined type data instead of being guessed.
Unsigned 64-bit values can exceed JavaScript Number’s exact range.

References

MessagePack specification