The use of canonical tags to help solve the issue of web pages with valid duplicate content is now very well known, thanks to the announcement made by Yahoo, Bing, and Google last year that they would all be supporting canonical tags. However, more than a year later, the simple fact is that Google is the only one that has backed up its word and fully supports the attribute.
As of June this year, the last information we can find from Bing is that while it can understand the canonical tag, it does not interpret it as a command but only as a “hint”. This means that they do not necessarily “obey” the tag so that non-preferred URLs can still end up ranking better than your preferred URL. Bing’s algorithm will still be the one to determine which URL they will consider to be the primary URL. While Google also says that using the canonical tag does not always guarantee that they will follow the preferred URL at all times, it is obvious that they follow it most of the times. Even Yahoo seems to be doing better than Bing when it comes to clearing up the issue of primary URLs using canonical tags. Bing, however, has to catch up and take the canonical tag as more than a “hint”.
Despite the lack of full support of the canonical tag by Bing, it is still clear that its use is well worth it, especially since Google still rules the search world.