MessagePack Converter
Convert JSON to MessagePack binary and back in your browser. Hex preview, byte count, .msgpack file download.
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What is MessagePack Converter?
A MessagePack converter that turns JSON documents into MessagePack binary and back. It shows the encoded bytes as a hex dump with a byte count, lets you download a real .msgpack file, and decodes hex dumps into pretty-printed JSON. Everything runs locally in the browser.
Key Benefits
- Smaller payloads than JSON for API and IoT traffic
- Type fidelity: integers, floats, and binary stay distinct
- No upload - sensitive payloads never leave your machine
- Instant reverse conversion with one Swap click
Common Use Cases
- •Inspecting MessagePack blobs stored in Redis
- •Debugging binary payloads from IoT devices and MQTT brokers
- •Preparing compact request bodies for RPC APIs
- •Learning how JSON maps onto MessagePack byte formats
How to Use the MessagePack Converter
- Choose a direction: Pick JSON to MessagePack to encode, or MessagePack to JSON to decode.
- Paste your input: Enter a JSON document, or MessagePack bytes as hex (spaces, commas, and 0x prefixes are all accepted).
- Click Convert: The tool shows the hex encoding with its byte count, or the decoded pretty-printed JSON.
- Copy or download: Copy the output to your clipboard, download a .msgpack binary file, or use Swap to convert back instantly.
Key Features
- Two-way conversion: JSON to MessagePack and MessagePack to JSON
- Hex preview of the encoded bytes with an accurate byte count
- Download the result as a .msgpack binary or .json text file
- Full spec coverage: fixint, fixstr, fixarray, fixmap, 8/16/32/64-bit integers, floats, and bin types
- Runs 100% in your browser - no upload, no API, works offline
- Swap button moves the output back into the input for instant reverse conversion
Frequently Asked Questions
What is MessagePack?
MessagePack is a compact binary serialization format. It represents the same data structures as JSON (objects, arrays, strings, numbers, booleans, null) but encodes them as bytes, typically producing smaller payloads that parse faster.
Is my data uploaded anywhere?
No. The encoder and decoder are implemented in pure TypeScript and run entirely in your browser. Nothing is sent to a server, so the tool also works offline.
Which MessagePack types are supported?
All core types: positive and negative fixints, 8/16/32/64-bit signed and unsigned integers, float32 and float64, fixstr and str 8/16/32, fixarray and array 16/32, fixmap and map 16/32, booleans, nil, and bin 8/16/32 (shown as hex).
Why do large 64-bit integers lose precision?
JavaScript numbers are 64-bit floats, which can only represent integers exactly up to 2^53 - 1. Values beyond that are approximated when decoded back to a JavaScript number.