> From those 5 characters you can determine the city, the state, and the country
False. Many zip codes include more than one city, and some even cross multiple states. And you can't always tell the difference between codes from different countries. Now you're not just instantly filling the rest of the form, you're implementing fancy multi-country filtering logic, editable drop downs, etc. Given the obvious incompetence of the people implementing most web forms, you're asking for disaster here.
Instead, learn to use your browser's autofill feature, and design your sites with it in mind. If you do it right the user literally doesn't have to type a single character. That's even better than typing a numeric code. Sadly even this seems beyond the abilities of the people who implement web forms.
False. Many zip codes include more than one city, and some even cross multiple states. And you can't always tell the difference between codes from different countries. Now you're not just instantly filling the rest of the form, you're implementing fancy multi-country filtering logic, editable drop downs, etc. Given the obvious incompetence of the people implementing most web forms, you're asking for disaster here.
Instead, learn to use your browser's autofill feature, and design your sites with it in mind. If you do it right the user literally doesn't have to type a single character. That's even better than typing a numeric code. Sadly even this seems beyond the abilities of the people who implement web forms.