Why do some sites block autocomplete on emails?

Question

As a regular and frequent online shopper I have noticed that quite a few sites switch off autocomplete on email fields.

For me this doesn't make too much sense, I am more likely to make a mistake typing my email than selecting it from an autocomplete list (indeed, many sites also just use one field for email without confirm, exacerbating this potential problem), not to mention it slows me down. While I have no evidence to back this hypothesis up I would be surprised if I was the only one who is like this.

What is the rationale behind the decision to do this during more critical online interactions like checking out or logging in ?

Answer 1

One of the reason that jumps to mind straight away is security. Having forms auto-complete is all well and good, when it's your own personal PC, which no-one else is going to use. However in places such as a internet-café, or a public library, where you can share computers with any number of people, you're unlikely to want your email address being shown to everyone else who uses the computer after you.

Ideally, yes, the computer should be setup to clear saved form data after the browser closes, but there's no guarantee it will be, so by setting it to be disabled the site is ensuring your account is that little-bit more secure.

Modern browsers will also not offer to save the username/password combo for a login form if auto-complete is disabled, so there's the added benefit of the user not accidentally selecting to save the Un/PW on the public machine if they're less than tech-savvy (or just genuinely mis-clicked).

Answer 2

There's nothing more to say but: because their UX is bad.

As you mentioned, the autocorrect function decreases a chance of making a typo in the e-mail address field, as well as confirmation field does. I've done a 20 minute research on most popular e-commerce I personally use and I didn't see a single example of the aforementioned UX design. It's definitely a bad practice.

The only rational reason for this I can actually imagine is that some of these sites you mean use some template systems that make such modifications as modifying single HTML field difficult (as a front-end developer, have met seen before, especially if speaking about modifying someone else's code...).