If your web app has separate database fields for first name and last name, you are doing it badly wrong. I'm looking at YOU, practically every Silicon Valley tech startup.
@Floppy Hm yeah I see. I guess the safer way to go about it is indeed having a single text field and dumping whatever they type in the database, with some sensible length limitations.
@noeldemartin https://www.kalzumeus.com/2010/06/17/falsehoods-programmers-believe-about-names/ is a good read - given all that I use a single field for name, and ask for other specific (e.g. "how should we address you") if necessary.