HTML for Numeric Zip Codes

I just overheard this discussion on Twitter, kicked off by Dave.

It seems like zip codes are just numbers, right? So...

<input id="zip" name="zip" type="number">

The advantage there being able to take advantage of free validation from the browser, and triggering a more helpful number-based keyboard on mobile devices.

But Zach pointed out that type="number" is problematic for zip codes because zip codes can have leading zeros (e.g. a Boston zip code might be 02119). Filament group also has a little lib for fixing this.

This is the perfect job for inputmode, as Jeremy suggests:

<input id="zip" name="zip" type="text" inputmode="numeric" pattern="^(?(^00000(|-0000))|(\d{5}(|-\d{4})))$">

But the support is pretty bad at the time of this writing.

A couple of people mentioned trying to hijack type="tel" for it, but that has its own downsides, like rejecting properly formatted 9-digit zip codes.

So, zip codes, while they look like numbers, are probably best treated as strings. Another option here is to leave it as a text input, but force numbers with pattern, as Pamela Fox documents:

<input id="zip" name="zip" type="text" pattern="[0-9]*">

As many have pointed out in the comments, it's worth noting that numeric patterns for zip codes are best suited for the U.S. as many the codes for many other countries contain numbers and letters.