International address validation is the process of comparing a non-US address against the authoritative address database from the country in question. Much like validating addresses in the United States, an international address is validated when a match is found in that country's address database, and it fails to validate when their is no match. Things are complicated a bit by the fact that international databases aren't always organized as nicely as the one we have at the USPS. But that doesn't mean it isn't possible.
Not every validation provider offers international address verification. It can be expensive to acquire the data, whether first-hand or second-hand. It can be costly to check against the database in the first place, and it can be difficult to write the code that teaches the program how to differentiate and sort through all the different address standards involved in standardizing an international address.
But we do it, and that's because we like a challenge, we like making difficult things easier, and because the world isn't going to validate itself.
First, some basics. Those of you who have dealt with domestic address validation (or at least US validation, for those of you living outside the US) will notice some differences in the international process.
For instance, there's not always clear, cut-and-dried division lines between segments of a country. What we call "states" in the US (it's where the "S" part comes from), and what are sometimes called "provinces" elsewhere, are often termed "administrative areas" in places that use neither term. Why is that important? Because even if there are no clearly-defined "states" in a country, the postal service still needs to know which section of the nation it's going to.
Then there's the issue of language. A lot of the world uses Latin characters, like the ones you're reading now. A lot of the world doesn't. That can cause some problems, so providers like us usually try to simplify the interface to make things easier on you. Here's how we handle it: if you don't specify output characters, the data will be returned in the same ones you used to enter the addresses. If you specify "native," it will return the characters native to that country's language. And if you specify "Latin," it will return Latin characters. (And if non fueris locutus Latin, don't worry—it's only the characters, not the language.)
Another detail is including the country of destination in the input. In order to properly validate, a value designating the destination country must be included in the input. This can either by the country's full name, or an ISO Classification There are three formats currently accepted: ISO-2 (a two-letter abbreviation similar to state abbreviations in the US), ISO-3 (a three-letter abbreviation), and ISO-N (a numeric code assigned to the country). One of these options must be included with the address, or it will fail to validate, regardless of its existence—or lack thereof—in the system.
Knowing what international address validation is isn't as important as knowing what you expect from international address verification. Do you want to know that the full address is valid and deliverable? Or are you only interested in knowing whether the city or street portion of the address is valid?
The United States has an incredibly organized postal system. Think about it; there's over 150 million delivery points for the USPS nationwide, and the USPS delivers mail daily. That means if everyone got a letter on the same day, the guys and gals in blue shorts would be making 150 million stops on that day alone.
Not every country is that organized.
For most countries there is no such thing as Delivery Point Verification (DPV). Many local postal services just doesn't have the data at that level. In fact, out of 241 mailing entities (which is "technically" more than there are official countries in the world, mind you), there are only 12 that even have delivery point data available: Austria, Belgium, Canada, Finland, France, Germany, Netherlands, New Zealand, Singapore, Sweden, United Kingdom, and United States.
52% of the world can't even tell you if the street in the address is real; another 25% can, but that's the best they can do. If you're curious how mail gets to people in places like that, it's simple: the postman personally knows where to take it, but that information isn't recorded at the local post office.
This can be caused by a number of different factors, but one of the big ones is political upheaval. Postal services are usually a function of the government, and when the government is in flux, so is the organization that runs the post. If the mailman has more than barking dogs to worry about, sometimes that means no delivery service—at least, no reliable service.
Here's the good news: the accuracy thresholds vary by country. Why is that good news? The majority of addresses that are processed for address verification are ones from the countries with established postal systems.
Here's more good news: we at SmartyStreets offer international address validation. So whether at home or abroad, we can help you get the validation you need.