Today is world IPv6 (Internet Protocol version 6) day, and sites like Facebook, Google, and Yahoo are among the Internet’s big names participating in a 24-hour test for the latest version of the web. Back in February, ICANN doled out the very last IPv4 addresses, signifying that the WorldWideWeb template as we knew it had run out of room. Of course, this isn’t the Internet apocalypse that it sounds like: At its most basic this means we used up all four billion IP addresses available with IPv4, and now it’s time to get some new ones via IPv6.

In truth, nothing is seriously changing for end users for some time.  Today simply marks the initial testing for large Internet companies who are now offering their sites over IPv4 as well as IPv6 (you can check out a list of all the participating companies here). On its blog, Google explains that users will either access sites over IPv6 without any hiccups, and if one occurs they will just fall back to IPv4, likely without being any the wiser. You can test your IPv6 connectivity here.

But how’s the test run going so far? So far, everyone using IPv4 is able to access the major sites being tested just fine. Unfortunately, a sampling of UK Internet users shows that 94-percent of sites aren’t working as they should be, and 92-percent are working over IPv6 at all. But luckily, no one’s broken the Internet and this sample go at it should help iron out the issues.