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ToolWrenPaste a CoAP packet as hex bytes to break it down into its header fields, token, options and payload. Useful for IoT debugging and learning the Constrained Application Protocol (RFC 7252).
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0x are ignored).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.
The Constrained Application Protocol (CoAP) is a lightweight, RESTful protocol defined in RFC 7252 for constrained devices and networks (IoT). It runs over UDP and mirrors HTTP concepts — GET, POST, PUT, DELETE and response codes — with very low overhead.
Every message starts with a fixed 4-byte header: a 2-bit Version, 2-bit Type (CON, NON, ACK, RST), 4-bit Token Length, an 8-bit Code (e.g. 0.01=GET, 2.05=Content) and a 16-bit Message ID. The header is followed by the token (0–8 bytes), then options in delta-encoded TLV format, then an optional payload preceded by the 0xFF marker.
Options use delta encoding: each option's number is the previous number plus the 4-bit delta nibble. Nibble values 13 and 14 signal one- or two-byte extended fields. This decoder resolves common option numbers (Uri-Path, Content-Format, Observe, etc.) and renders string/uint values where appropriate.
0x prefixes are ignored, so 41 01 12 34 and 41011234 both work.class.detail. Class 0 = request method (0.01 GET, 0.02 POST, 0.03 PUT, 0.04 DELETE). Class 2 = success (2.05 Content), 4 = client error, 5 = server error.