[msla]

For the American case, the USPS has a free API to do address validation and standardization.

USPS APIs in general:

https://www.usps.com/business/web-tools-apis/#dev

https://www.usps.com/business/web-tools-apis/documentation-u...

The specific API:

https://www.usps.com/business/web-tools-apis/address-informa...

[michaelcampbell]

FWIW, I've used this API for some years. On the con side, it uses XML, but on the pro side, it's fast, reliable, and consistent. And free, at least for my volumes.