Validate or generate the XOR checksum for any NMEA 0183 sentence, with step-by-step XOR.
Your vote is saved on this device only.
Paste any NMEA 0183 sentence and this tool computes its XOR checksum, then compares it against the two hex digits after the asterisk to confirm the sentence is intact. It works in both directions: validate a received sentence or generate the correct checksum for one you are building, with a step-by-step XOR breakdown showing how each character between the "$" and "*" folds into the final value.
It is built for marine electronics technicians, AIS and GPS developers, and anyone parsing or crafting sentences like GPGGA, GPRMC, or proprietary messages. The calculation runs entirely in your browser, so your sentences are never uploaded anywhere. It is free, needs no sign-up, and once loaded works offline.
It is the XOR of every character between the leading "$" (or "!") and the trailing "*", expressed as two hexadecimal digits. The tool performs this XOR and shows the result.
No. The $ or ! start delimiter and the * before the checksum are excluded. Only the characters in between are XORed together.
Yes. The tool computes the correct checksum from the data and you can compare it to the existing one after the asterisk to confirm whether the sentence is valid.
Yes. Encapsulated sentences such as !AIVDM use the same XOR rule between the "!" and "*", so the calculation applies identically.
No. Everything is computed locally in your browser, nothing is uploaded, and the tool keeps working offline once the page has loaded.