It's "it's" and "its" for me. My RoT is make the apostrophe into an "i", and see if the sentence still works.
The "horriblest" abuse I've seen was a British author writing about a young man who was an English Major in college, but did "U-Chooz". All the "its" and "it's" were "its' " 😲 ("itses"? Sounds like Gollum, yes it does, my precious!)
And (at no extra charge!) the article missed "yore"! "Your father said, 'Pretend you're in days of yore.'")
--Rich