Will Apple Watch record AFIB?

While the monitor on the watch will display your heart rate, it does not record like an EKG instrument, as the watch is not a certified medical device. It will show your rate, and if you feel you are experiencing an incident, you can get it to record your rate again, otherwise, all it does is record a specific intervals on a regular basis. It is not set to be able to recognize a change in the rate and then record.

Understand, that you can go to the Health App and view the rates that have been recorded for the day. I believe the regular interval of the checks is around 10 minutes. See this support document for a little better explanation. Measure your heart rate with your Apple Watch - Apple Support This gives you some info, but not extremely detailed for a heath care professional.