That's just the navigator.userAgent. You can add it as a hidden field to form posts.
Note users will have multiple values as they move across devices. It's up to you whether to store all (in a history field) or one. I'd store all.
Ah perfect! Didn't realize it's something I could have just populated as a hidden form field. I'm going to go ahead with that route.
And good heads up on the multiple values aspect, i'll take that into consideration.
Thanks so much!!