CBOR Encoder/Decoder
Encode JSON to CBOR bytes and decode CBOR back to JSON in your browser. Full RFC 8949 support for WebAuthn, COSE, IoT, and CBOR Web Tokens. Free and private.
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What is CBOR Encoder/Decoder?
CBOR (Concise Binary Object Representation, RFC 8949) is a compact binary data format used in WebAuthn, COSE, IoT, and CBOR Web Tokens. This tool lets you encode JSON into CBOR bytes and decode CBOR back into readable JSON, entirely in your browser.
Key Benefits
- Two-way conversion between JSON and CBOR bytes
- Full RFC 8949 support including byte strings, bignums, and tags
- Smart float encoding for compact, exact output
- Accepts hex or Base64 input on decode
- 100% client-side — no data leaves your device
Common Use Cases
- •Inspect WebAuthn attestation and assertion payloads
- •Decode COSE and IoT (SenML) messages
- •Debug CBOR Web Token (CWT) contents
- •Encode configuration or API data into compact CBOR
How to Use the CBOR Encoder/Decoder
- Choose a mode: Click Encode to convert JSON into CBOR bytes, or Decode to convert CBOR bytes (hex or Base64) back into readable JSON.
- Enter your data: In Encode mode, paste valid JSON like {"hello":"world"}. In Decode mode, paste hex bytes (e.g. a16468656c6c6f65776f726c64) or Base64.
- Read the output: Results appear instantly. Encode shows Base64 and spaced hex bytes. Decode shows pretty-printed JSON and the original hex bytes.
- Copy the result: Click Copy next to any output field to copy the Base64, hex, or JSON value to your clipboard.
Key Features
- Two-way conversion: encode JSON to CBOR bytes and decode CBOR back to JSON
- Full RFC 8949 support: integers, byte strings, text, arrays, maps, floats, booleans, bignums, and tags
- Smart float encoding — prefers half-precision (16-bit), then single (32-bit), then double (64-bit) for exact round-trips
- Accepts hex or Base64 input on decode; shows byte strings as both hex and Base64 on encode
- Real-time results as you type
- 100% client-side - no data uploaded, ideal for inspecting WebAuthn and IoT payloads