That was just a simple example. If you take addresses as a whole, it gets a hell of a lot more complicated. I do agree that you can just `[ -]` in the middle of

That was just a simple example. If you take addresses as a whole, it gets a hell of a lot more complicated. I do agree that you can just `[ -]` in the middle of that one, but simple examples are simple. Also, it's telling that very few sites actually do this. The real point is that you want to have one regular form for the input in your database, but imposing that one that you prefer on your users creates friction when their experience of the world differs. As for 0 vs. O, in a Canadian postal code it doesn't matter, because there is indeed a very regular language to them: letters alternated with numbers. A round circly thing in a numeric position is a 0 and a round circly thing in a letter position is an O. No matter what. The only time this actually indicates a problem is if the pattern ceases to hold after the round circly thing, in which case it may or may not be the 0/O confusion that's the problem but it was wrong anyways. I'm not saying you should store it wrong, but if a user enters "HOH-OH0" and you ask "did you mean 'H0H 0H0'?"[1] and they say yes then you've given the user a much better and helpful flow than "Invalid Postal Code, please fill out the form again." [1] This is a 'real' postal code btw and it goes to a weird santa-letter black hole even though it doesn't indicate a geographical location that corresponds to the north (an H prefix is for Montreal).