While you should always watch out for weird site-name changes, in this case you don’t need to worry. The number probably just means the site you’re browsing is using a slightly old-school load-balancing technique. You’re still on the same site, but your traffic is being directed to a particular server because the others are busy.
What is WWW anyway?
WWW is a hostname or something that identifies a device on a network, and it used to be a way to specify that you wanted to go to the server holding a website’s webpage, as opposed to the email server or some other part of the site. The WWW in “www.example.com” would get you to the webpage, while “ftp.example.com” would get you to the FTP server and “mail.example.com” might get you to the mail server. We don’t really need to specify this anymore, since webpages are by far the most popular thing on the Internet, and most servers will just automatically direct you there without you needing to specify that you want to visit the web server. It’s still hanging around as a convention, though, and you can keep typing it in if you’re so inclined – you’ll get to the same page regardless of whether you specify the WWW or not.
Why do some sites seem to need WWW[number]?
Even though it’s an unnecessary naming convention, some sites, especially larger and older ones, use the WWW[number] format as a way to name subdomains (separate sections of the same site, but not necessarily on separate machines) or as hostnames for different physical servers. In the latter case, this is probably a load-balancing technique. Each server can only handle so many users, so when you visit a site by typing in the address, with or without the WWW, your request might hit a load balancer that checks the status of each server and decides to route your traffic towards, say, the WWW3 subdomain.
It might also mean that their main server is having trouble, and you’re being sent to a backup, or it could mean that there’s some sort of a test or update going on, or maybe they’ve just decided WWW3 is the way to go. Either way, you’re essentially visiting the same site, even though if you try to get back to www3.example.com later, the load balancer might bounce you back to the main www.example.com site.
So no worries then?
It’s hard to tell what’s going on behind the scenes by just glancing at the WWW prefix, but as long as the domain name is the same, you don’t typically need to be concerned about alternative hostnames or subdomains. You probably won’t see very many sites using this anymore, since there are more sophisticated load-balancing techniques now available that mostly work behind the scenes, but there’s nothing inherently insecure about adding numbers to your WWW, and if a site has been working well with this method, they just might not see the point in changing it. Indeed, it often pops up on banking websites, which use different subdomains for security and may have named them with the WWW convention.
