Loading CoAP Decoder...
Decode a CoAP (RFC 7252) message into its header, code, options and payload. Paste the raw bytes as hex or base64. Everything runs in your browser.
CoAP is the lightweight REST-like protocol for IoT, running over UDP. This decoder reads the 4-byte header (version, type, token length, code, message ID), the token, the delta-encoded options (Uri-Path, Content-Format and friends) and any payload after the 0xFF marker.
Decode a CoAP (RFC 7252) message into its header, code, options and payload. Paste hex or base64. Runs entirely in your browser.
CoAP, the Constrained Application Protocol, is a lightweight REST-like protocol for IoT devices that runs over UDP. Its compact binary messages are efficient on the wire but unreadable when captured raw. This tool parses a CoAP message and shows the version, message type, method or response code, token, options such as the request URI path, and any payload.
Input:
40 01 12 34 b4 74 65 6d 70
Output:
CON, 0.01 GET, Message ID 0x1234, Uri-Path: temp
What message types are decoded?
All four: CON (confirmable), NON (non-confirmable), ACK (acknowledgement) and RST (reset), along with the request methods and response codes.
Which options are recognised?
The common ones including Uri-Host, Uri-Path, Uri-Query, Content-Format, Accept, ETag, Observe and Max-Age. String and integer options are decoded; others are shown as hex.
Does it handle the payload?
Yes. Anything after the 0xFF payload marker is shown as text when it is valid UTF-8, otherwise as hex.
Is anything uploaded?
No. The packet is decoded entirely in your browser.