Here's another input filtering bad practice that most US front-end devs don't seem to know about (but really should when they build global websites)

Don't assume a specific keyboard layout when you're trying to filter out non-numeric values in a text field

I use a French keyboard, and numbers on the top keyboard row are accessed with Shift. A unmodified keypress in this row is for various accented characters, quotes, parentheses and a few others. In other words, it's the opposite of a US/UK keyboard.

Almost every week I come across a website (including a large US stock broker) whose numeric fields seem to block out modifier keys. I have to switch my Macbook to US layout just to type those in (because conveniently, they also disable pasting in those fields of course)

This is very widespread (is that part of a popular front-end framework maybe ?) and difficult to report, because most devs in English-speaking countries never experience the issue first-hand.