What is Google Autocomplete?

Google Autocomplete speeds up the checkout by reducing the number of keystrokes and offering suggestions as the user types. It looks like this:

What is Address Validator?

Address Validator checks addresses for deliverability to mitigate failed deliveries and delays in shipping. It looks like this:

Address Validator checks for deliverability

Autocomplete issue #1: Addresses missing apartment numbers

Many city addresses require an apartment number and omitting this component often results in a failed delivery. Address Validator checks to make sure an apartment number is specified when necessary, Google Autocomplete does not.
 
For example, Infinity Towers in San Francisco has 650 units and is located at 301 Main Street. Google Autocomplete does not offer any suggestions with apartment numbers. Some customers may select an address from the list and forget to specify the unit number:

Address Validator issues a warning if the customer proceeds without an apartment number: 

Autocomplete issue #2: Non-existent addresses

Some customers accidentally transpose two characters. For example, they may type in "310 Main Street" instead of "301 Main Street". The former does not exist and will result in a failed delivery.

Google Autocomplete does not check to make sure the address exists. For example, 300000 Main St does not exist, but Google Autocomplete still populates a list of addresses for the customer to select:

Address Validator issues a warning if the customer proceeds with an address that does not exist:

Autocomplete issue #3: Missing street number

Some customers may choose suggestions without street numbers, resulting in failed deliveries: