Web Authoring Statistics: Link Relationships

HTML has two link relationship attributes, rel and rev, which apply to the link and a elements. What values are most used?

stylesheet, icon, shortcut, alternate, and next.

Methodology: The analysis counted separate keywords in the same attribute as separate keywords, so for example rel="a b" counted as one a keyword and one b keyword; with one exception: if alternate and stylesheet were specified on the same link element's rel attribute, then that was counted as one stylesheet alternate keyword instead.

From these results we can see that the most common relationship by far is <link rel="stylesheet">, which isn't surprising, but we can also see that the second most common link is the one that gives custom favicons for the page (rel="SHORTCUT ICON" to be compatible with IE, or just rel="icon" if it is only intended to work on the other browsers — hence the two values in the results, and hence the slight difference in frequency). In other words, the two most common link relationships (by far!) are presentational.

The rel="alternate" value is mostly RSS feeds, rel="edituri" is a blogging autodiscovery value, and the rel="service.post" value that barely scrapes into the top 20 is part of the Atom API. We can therefore determine that blogs are not a negligible part of the Web these days (and that Atom is reaching relatively wide deployment, given that it is still a young technology).

An interesting thing to note from this is that the only <a rel=""> value to appear on the list of the top 20 relationships is Google's rel="nofollow", and the only <link rev=""> link to appear is rev="made" (to point to the author's page) — and the latter is not used that much more than the more sensible rel="author". Also, ironically, just off the graph in position 21 is rel="made", probably showing that the distinction between rel and rev may be too subtle for many authors. More evidence of this is at position 29 on the list, with <link rev="stylesheet">. The first <a rev="">, rev="made">, appears on the list at position 96, beyond the point of statistical clarity.

The rel="file-list" value is part of Microsoft Office's HTML output.

Alternate stylesheets (which were specifically counted separately — the rel="stylesheet" and rel="alternate" entries don't include rel="alternate stylesheet" entries) are, surprisingly, in the top 20 (barely). They don't seem that popular, though, relative to normal stylesheets.

Not shown above, but 33rd on the list, is rel="pingback", of the Pingback Specification, written in 2002. Around the same time, Tantek Çelik was recommending that people use <a rel="bookmark"> for permalinks; they come in at number 39. (Oddly, <link rel="bookmark"> is used more, coming in 34th on the list.)