A URL, or Uniform Resource Locator, is a technical term for what is more commonly known as a website address. In a Web browser, the URL field is where a user can type or paste an address such as wisegeek.com. While domain names are not case-sensitive, the rest of the URL might be. In our example, this would be everything that follows “.com” as in wisegeek.com/are-urls-case-sensitive.htm.

A URL is a technical term for a website address.

Every website is hosted on a server, a type of computer that runs continuously to provide constant access to the websites it hosts. Servers running Windows® operating systems disregard case in URLs, interpreting identical spelling as being the same address. A server running a Linux® or UNIX® operating system, however, would interpret the two different capitalizations as pointing to two different page addresses. This could be a problem for some webmasters.

For example, a person named Jack has designed a website for gamers. Jack’s hypothetical site features blog pages, news, tips, cheats, and forums, is many pages deep and has built up quite a following over the years, funneling through several thousand visitors a day. When Jack was building the site, he used mixed-case lettering to name each page, such as “TipsandTricks.html,” because it was easier to read than “tipsandtricks.html.” In the embedded links, he used small case to point to pages. Other websites that point to Jack’s pages might also use small case lettering.

One day, Jack gets an email that his host service will be upgrading their servers, migrating websites to newer machines. Jack notices that once this happens, his traffic falls off significantly on many of his pages. Since his address hasn’t changed, Jack might wonder what’s happened.

If the new computers are running Linux® or UNIX® operating systems, Jack’s URLs would suddenly become case-sensitive, as would any folders he created on his website. Links to “.../tipsandtricks.html” would result in a 404 error page — a message announcing that the page could not be found. Over time, search bots would make the correct connections, but revenue and traffic would be lost in the interim. To correct the situation, he could request his host allow him to edit the 404-error page so that it forwards visitors to the correct addresses.

This case-sensitive rule also applies to folders. If a webmaster creates a folder on a Linux® or UNIX® host server, as “.../html/Folder1/” this is different from “.../html/folder1/” and none of the pages contained within said folder will be accessible to the Internet without the proper case specified in the embedded links.

While Microsoft® operating systems have dominated public servers, making case-sensitive URLs less of a consideration, this could be changing. Linux® provides attractive alternatives and the popularity of open source software continues to grow. Today’s webmasters will ideally create addresses, embedded links, and folders that can easily slide from one host or operating system to another. This should ensure traffic and revenue retention and make for a stress-free migration for webmasters and visitors alike.