Submitted by Urgettingfat t3_126dpbj in LifeProTips
One of my callings in life seems to be to address this common typo that I find within the places I'd least expect. It's annoying to read from a place from where I'm expecting credibility and consistency, only to find its writers making this same mistake all over their website or posts. The source of the typo comes from its counter-intuitive rule, where normally, to show possession, the word's suffix is appended with an s, using an apostrophe. However in this rare case, the very same word (it) has the ability to also be concatenated with another word (is). So this one time, when it's to show possession, its apostrophe is omitted, so that it can be distinguished from when it's being concatenated. For those who actually read this, thank you for your time and good day.
beeweeird t1_je8selm wrote
An easier way to remember it is that you only use "it's" if you can replace it with "it is". Otherwise, use "its".