ToolWren › CBOR

CBOR Decoder

Paste a CBOR (Concise Binary Object Representation) payload as hex to decode it into readable JSON. CBOR is the compact binary cousin of JSON used widely in IoT.

100% client-side · nothing is uploaded

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How to use the CBOR

Paste your CBOR payload as hexadecimal bytes into the Input box.
The decoded JSON appears automatically in the output.
Byte strings are shown as hex inside a $bytes wrapper.
Click Copy to copy the JSON result.

Privacy: this tool runs entirely in your browser. Your input is never sent to, received by, or stored on any server — there are no uploads and no tracking of what you enter.

About CBOR

What is CBOR?

CBOR (RFC 8949) is a binary data format that models the JSON data set but is far more compact and faster to parse. It's the payload format behind COSE, CWT and many CoAP/IoT applications.

How decoding works

Each CBOR item starts with an initial byte encoding a major type (integer, string, array, map, etc.) and a length or value. This tool walks the bytes and reconstructs the equivalent JSON structure, showing byte strings as hex.

When to use it

Decoding CBOR is essential when debugging constrained-device messages, inspecting CWT tokens, or reading the payload of a CoAP response that uses application/cbor.

Frequently asked questions

What input format is expected?

Hexadecimal bytes. Spaces, newlines and 0x prefixes are ignored.

How are byte strings shown?

As an object like {"$bytes":"..."} containing the hex, since raw bytes have no direct JSON equivalent.

Does it support indefinite-length items?

Not yet — streamed/indefinite-length CBOR is uncommon in IoT payloads and is reported as unsupported.

Is my data uploaded?

No. All decoding happens in your browser.