MessagePack to JSON

What it does

Decodes a MessagePack blob into readable JSON. Paste the bytes as hex — spaces are fine — or open a file, and the JSON appears beside it. It encodes the other way too: JSON to MessagePack hex.

Why decode it here

MessagePack is binary, so inspecting one usually means pasting raw bytes into an online decoder — uploading the contents of a Redis value, a websocket frame, or an RPC payload to a third party. This does it in your browser, so the bytes stay on your machine.

64-bit integers stay exact

MessagePack has a real 64-bit integer type that JSON numbers cannot represent without rounding. Values past 2⁵³ are shown as strings so their exact digits survive instead of collapsing to a nearby float, and encoding back preserves them.

When to use it

Reading a MessagePack value out of Redis, a cache, or a message queue, debugging a websocket or RPC frame, or confirming what a client actually sent on the wire.

Privacy

Both directions run in your browser. Nothing you paste is uploaded, and the page works offline after the first load.