MessagePack Parser

MessagePack is an efficient binary serialization format, like JSON but smaller and faster. It's used in Redis, Fluentd, and many RPC systems. This tool parses MessagePack files and displays the contents as JSON with metadata about types and sizes.

Specifications

• MessagePack Specification
• msgpack.org

Common Use Cases

• Debug MessagePack-encoded API responses
• Inspect Redis cached data serialized with MessagePack
• Analyze Fluentd log messages
• Convert MessagePack to JSON for logging or debugging
• Understand RPC payloads in MessagePack format

Features

• Parse MessagePack binary files via drag-and-drop or file selection
• Decode hex-encoded MessagePack data
• Support all MessagePack types including extensions
• Convert to JSON for readability
• Show document metadata (size, type counts, max depth)
• Display extension type information
• Handle binary data and timestamps
• Hex viewer for raw binary inspection

Examples

82 a5 68 65 6c 6c 6f a5 77 6f 72 6c 64 a5 63 6f 75 6e 74 2a

83 a4 6e 61 6d 65 a5 41 6c 69 63 65 a3 61 67 65 1e a6 61 63 74 69 76 65 c3

Tips

• You can paste hex-encoded MessagePack data directly to parse it.
• MessagePack is typically 50-80% the size of equivalent JSON.
• Extension types (negative type codes) are application-defined.
• Timestamps use extension type -1 with various precision formats.
• Some implementations use extension type 1 for timestamps.

Understanding MessagePack

MessagePack is a binary serialization format that aims to be as compact as possible while maintaining JSON-like data model compatibility. Created by Sadayuki Furuhashi, MessagePack encodes data in a self-describing binary format where type information and data are interleaved, allowing efficient parsing without an external schema.

The format uses a variable-length encoding scheme. Small integers (0-127) fit in a single byte. Short strings include their length in the type byte itself. Maps and arrays use compact length prefixes. This design typically produces payloads 50-80% the size of equivalent JSON, with significantly faster serialization and deserialization because there is no text parsing overhead.

MessagePack supports nil, boolean, integer (signed and unsigned up to 64-bit), float (32 and 64-bit), string, binary, array, map, and extension types. Extension types allow applications to define custom types — the timestamp extension (type -1) is the only standardized extension. Libraries exist for virtually every programming language with consistent cross-language compatibility.

MessagePack is used in Redis (as an optional serialization format), Fluentd (log forwarding), SignalR (real-time web), and many RPC systems and game networking protocols where bandwidth and parsing speed matter. It is a good choice when JSON compatibility is desired but the overhead of text serialization is too high.

MessagePack is best suited for scenarios where bandwidth or parsing speed is critical: real-time communication, high-throughput APIs, game networking, IoT devices, and caching layers. JSON remains the better choice when human readability matters, for configuration files, or when interoperating with systems that expect text-based formats.

Compared to Protocol Buffers, MessagePack is schema-less like JSON — data is self-describing and can be serialized without a predefined schema. Protocol Buffers require a .proto schema file compiled into language-specific code, but produce smaller payloads and provide stronger type safety. MessagePack is the better fit for dynamic data without schemas, while Protobuf excels for well-defined API contracts where maximum efficiency is needed.

Extension types allow applications to define custom data types beyond the built-in set. Each extension has a type code (-128 to 127) and arbitrary binary data. The timestamp extension (type -1) is the only standardized extension and represents nanosecond-precision timestamps. Applications can define their own extensions for types like UUID, BigDecimal, or domain-specific objects.