How do I ensure autocomplete works for a specific field?

Question

How do browsers recognize if a particular field (like a username) should be prompted with autocompletes? Do they use some sort of regex to match the fields name attribute? Is there a standard I need to follow to ensure this?

I ask this because on some sites the browser fails to suggest any historical data.

Put simply, I am asking the exact opposite of what this person was trying to achieve:

How do you disable browser Autocomplete on web form field / input tag?

Answer 1

With HTML5:

 <form action="demo_form.asp" method="get" autocomplete="on">
 First name:<input type="text" name="fname" /><br />
 E-mail: <input type="email" name="email" /><br />
 <input type="submit" />
 </form>

Source: http://www.w3schools.com/html5/att_form_autocomplete.asp

Answer 2

In my experience it's based on matching the name or id attribute of the input tag. Which is why you generally find that username, email and name fields tend to autocomplete on a number of different websites.

I think the matching has to be exact, not a regex or partial match on the field.