The URL will continue to be part of the Web user interface for several more years, so a usable site requires:

  • a domain name that is easy to remember and easy to spell
  • short URLs
  • easy-to-type URLs
  • URLs that visualize the site structure
  • URLs that are “hackable” to allow users to move to higher levels of the information architecture by hacking off the end of the URL
  • persistent URLs that don’t change

In principle, users should not need to know about URLs which are a machine-level addressing scheme. In practice, users often go to websites or individual pages through mechanisms that involve exposure to raw URLs:

  • people guess the domain name of sites they have not visited before: if possible, secure the name of your company and main brands as domain names
  • even when people have been to a site before, they will often try to guess or remember the site name instead of using a bookmark or history list: have memorable domain names that are easy to spell
  • the social interface to the Web relies on email when users want to recommend Web pages to each other, and email is the second-most common way users get to new sites (search engines being the most common): make sure that all URLs on your site are less than 78 characters long so that they will not wrap across a line feed
  • shorter URLs are better since people often type them manually
  • do not use MiXeD case text in URLs since people can’t remember the difference between upper-case and lower-case characters: all-lowercase URLs are usually preferred (domain names are less of a problem since they are case-insensitive – usability would increase if webservers would ignore case in resolving URLs)
  • use a spelling-checking webserver to minimize the damage caused by the inevitable typos

Persistent URLs Attract Links
Links from other websites are the third-most common way people find sites (after search engines and email recommendations), so build your site to make it easy to attract inbound links:

  • Linkrot equals lost business: make sure all URLs live forever and continue to point to relevant pages.
  • Do not move pages around but keep them at the same URL: it is very annoying for authors of other sites when their links either stop working or turn into pointers to something different because the original page has been moved and replaced by something new. There can be reasons to reserve a special URL for the current edition of a column or other special content, but the article should be stored at a permanent URL from the start and this URL should be listed on the page that is accessed through the temporary or varying URL.

Update added 2007:

Edward Cutrell and Zhiwei Guan from Microsoft Research have conducted an eyetracking study of search engine use (warning: PDF) that found that people spend 24% of their gaze time looking at the URLs in the search results.

MSR used Microsoft’s own search engine (fair enough), but their results match what we found in our eyetracking research which included the current market leader as well as the #2 search engine in addition to MSN.

Users have evolved a firm model of search behavior which they apply
across search engines, which is why it’s probably a lost cause to make
a non-standard search user interface.

We found that searchers are particularly interested in the URL
when they are assessing the credibility of a destination. If the URL
looks like garbage, people are less likely to click on that search hit.
On the other hand, if the URL looks like the page will address the
user’s question, they are more likely to click.