Confusables fixes the words people actually mix up — its/it's, your/you're, then/than, who's/whose, lets/let's, there/their/they're, lose/loose, affect/effect, could of → could have, and the typos if/of and form/from.

It changes only the misused word. Everything else stays exactly as you wrote it, and when a sentence reads both ways it does nothing.

Or try one — a mistake from each rule:

• Its been a long day
• Your the best
• This went better then that
• Who's keys are these?
• Lets go now
• Their going to love it
• I could of helped
• Don't loose hope
• The affect was clear
• Most if them left early
• He came form the store
• Its been a long day at its-been.com