Address Validation Using the Google Maps API: A better way to enter addresses?
telnet80.com
telnet80.com
One single web service that can validate addresses for just about every industrialized country.
Also, if you are interested in seeing example "correct" addresses for many countries, see Address Doctor. http://www.addressdoctor.com/en/countries_data/countries5.as...
Both of these companies are leaders in their field.
However, I'm growing wary of "dependency sprawl", where the functionality of a web application is tied to an increasing number of other services. That said, as far as uptime goes Google is hard to beat.
One thing to keep inmind is the Geocoding limit. If this is used on a busy website, you'll need to build in checks:
For our company, we would have loved to use Google for all our web API needs for addresses, but we can't, due to corporate firewall restrictions and the map display restriction mentioned by a reader's comment on that blog entry. Also, don't mistake this for true address validation, which is expensive.
I've since moved on, and the backend database hasn't been updated in nearly a decade. But it works fairly well, and can take free-form addresses as input.
I'm surprised there aren't more such free services out there.