Reasons to Use Autocomplete
The HTML The autocomplete attribute lets the developer decide if they want to enable the user to have automated assistance in filling out the form. You can determine where you want the automated responses to come from. They can come from values the user entered previously or pre-configured values the developer has decided upon.
Administrative levels in addresses
address-level1 through address-level4)
describe the address in terms of increasing levels of precision within
the country in which the address is located. Each country has its own
system of administrative levels, and may arrange the levels in different
orders when addresses are written.
address-level1 always represents the broadest
administrative division; it is the least-specific portion of the address
short of the country name.
Form layout flexibility
Given that different countries write their address in different ways, with each field in different places within the address, and even different sets and numbers of fields entirely, it can be helpful if, when possible, your site is able to switch to the layout expected by your users when presenting an address entry form, given the country the address is located within.
Variations
The way each administrative level is used will vary from country to country. Below are some examples; this is not meant to be an exhaustive list.
United States
A typical home address within the United States looks like this:
432 Anywhere St Exampleville CA 95555
In the United States, the least-specific portion of the address is
the state, in this case "CA" (the official US Postal Service shorthand
for "California"). Thus address-level1 is the state, or "CA" in this case.
The second-least specific portion of the address is the city or town name, so address-level2 is "Exampleville" in this example address.
United States addresses do not use levels 3 and up.
United Kingdom
Address input forms in the UK should contain one address level and one, two or three address lines, depending on the address. A complete address would look like so:
103 Frogmarch Street Upper-Wapping Winchelsea TN99 8ZZ
The address levels are:
address-level1: The post town - "Winchelsea" in this case.address-line2: The locality - "Upper-Wapping" in this case.address-line1: The house/street particulars - "103 Frogmarch Street".
The postcode is separate. Note that you can actually use just the postcode and address-line1
to successfully deliver mail in the UK, so they should be the only
mandatory items, but usually people tend to provide more details.
China
China can use as many as three administrative levels: the province, the city, and the district.
The 6 digit postal code is not always needed but when supplied it is placed separately with a label for clarity. For example:
北京市东城区建国门北大街 8 号华润大厦 17 层 1708 单元 邮编：100005
Japan
An address in Japan is typically written in one line, in an order from the least-specific to more-specific portions (in reverse order to the United States). There are two or three administrative levels in an address. Additional line can be used to show building names and room numbers. The postal code is separate. For example:
〒 381-0000 長野県長野市某町 123
"〒" and following seven digits shows the postal code.
address-level1 is used for prefectures or the Tokyo Metropolis; "長野県" (Nagano Prefecture) is in this case. address-level2 is typically used for cities, counties, towns and villages; "長野市" (Nagano City) in this case. "某町 123" is address-line1 which consists of an area name and a lot number.