One of the first usability critiques of website is usually the lack of breadcrumbs. If a site doesn’t have breadcrumbs, it is immediately perceived as difficult to use. While the latter may be true, I don’t think it’s usually because there are no breadcrumbs. I’ll explain that later.
Wait, what are breadcrumbs?
Breadcrumbs are these things:
Homepage > Section > Sub-Section

Over the years, breadcrumbs have evolved from a suggested improvement into one of the main parts of a web page along with the page name, search box, navigation, content area, and footer. The breadcrumb is intended to help orient the user to the site’s organization and structure.
What does the research say about breadcrumbs?
In a 2007 Alertbox, Jakob Nielsen stated “breadcrumbs are not important enough for a dedicated study”. Personally, I think they are.
The best research to-date on breadcrumbs is a 2003 article in UsabilityNews (from Wichita State’s Software Usability Research Laboratory). Rogers and Chaparro built a gardening website and studied how users interacted with the breadcrumbs in a usability test. The researchers found that breadcrumbs were used 6% of the time when participants navigated the website. In other words, 94% of the time participants used other ways to navigate the website (e.g. the main navigation or back button).
It has been over 8 years since Rogers and Chaparro’s research, but the 6% statistic is hard to ignore. It seems likely that as the web has evolved, more people have become accustomed to seeing and using breadcrumbs. Nielsen claimed in 2007 that his group was seeing more and more people use breadcrumbs in their usability studies. I would estimate that breadcrumbs are now used about 10-15% of the time to navigate a website.
Are breadcrumbs important?
Yes.
Users expect to see breadcrumbs, especially on sites with deep information architectures. Even if users are only using breadcrumbs 10-15% of the time to navigate, they are still relying upon them when necessary. Make sure to follow the breadcrumb guidelines provided by Nielsen. I’d make a list of guidelines here, but it is important to understand some of the issues and reasoning that Nielsen provides. So, go read it.
If a website is missing breadcrumbs, it is generally perceived as difficult to use. In most cases, the website actually is difficult to use. But, it is usually not because breadcrumbs are missing. Sites without breadcrumbs are generally lacking attention to detail. Breadcrumbs are usually included with a well-designed website.
I do think that the importance of breadcrumbs is greatly exaggerated when it comes to web usability. There are much bigger things to worry about, such as understanding your site’s users, writing effective web content, developing an intuitive navigation, and meeting all user goals.