Simply works. I've been reading about how showing alt text on hover rather than only doing so for the title tag was actually something that only Internet Explorer did, but when I'm browsing sites from 20+ years ago they oftentimes have images that have alt text but not title (which is to say they were designed for IE since it was the dominant browser at the time). So this is great to have if only to get that extra little bit of the experience from those old pages.