CBOR to JSON

What it does

Decodes a CBOR (Concise Binary Object Representation, RFC 8949) blob into readable JSON. Paste the bytes as hex — spaces are fine — or open a file, and the decoded JSON appears beside it. It also goes the other way: JSON to CBOR hex.

Why decode it here

A CBOR payload is binary, so the usual move is to paste it into whatever online decoder turns up — which means uploading the raw bytes of a device message, a COSE/CWT token, or a cache entry to someone else's server. This decodes it in your browser instead, so the bytes never leave your machine.

64-bit integers stay exact

CBOR carries true 64-bit integers, which JSON numbers cannot hold without rounding. When a value is larger than 2⁵³ it is shown as a string, so the exact digits survive instead of silently becoming a nearby float. Encoding the other way preserves them too.

When to use it

Inspecting a CBOR message from an IoT or embedded device, reading a COSE/CWT token, debugging an API or cache that speaks CBOR, or checking what a library actually serialized.

Privacy

Decoding and encoding both run in your browser. Nothing you paste is uploaded, and the page works offline after the first load.