Yes, it’s true, Yahoo has a keyword match type that may as well be a mystery to most of the SEM world. It’s called the canonical match.

Princeton defines canonical as: reduced to the simplest and most significant form possible without loss of generality.

Luke's Match

Canonical versions of the keyword include basic misspells, plurals, and the keyword + noise words like “a” or “the.” Google and MSN’s exact keyword match type include only one form of the keyword advertised. To show for plurals or misspells under Google and MSN’s exact match, you must upload every single version of the keyword that you want.

Consider the following example for the keyword “tool.”

Google’s exact match maps to: tool

Yahoo’s standard match maps to: tool, tools, the tool, a tool, for tool, about tool… and possibly many other versions of the keyword and misspells

Therefore, Yahoo’s standard match is actually more like Google and MSN’s phrase match type, and Yahoo really doesn’t offer an exact match type at all!

On a side note, Yahoo’s advanced match type is very much like Google and MSN’s broad match, which includes the keyword plus anything the system thinks is closely related to the keyword. For instance, the keyword “tool” might map to: tool, keyword tool, Google tool, SEM tool, and many other relevant versions of the keyword.

There is no way to turn the canonical mapping off and unfortunately, Yahoo doesn’t allow advertisers any exposure into the canonical mapping technology before keywords are uploaded.

The basic problem, however, with the canonical mapping is that you can unknowingly upload keyword duplicates into your account several times via different adgroups. For instance, if you upload the keyword “tool” into one adgroup, but upload “tools” into another adgroup, you will in result have the keyword duplicated in your account. This may not seem like a huge issue at first glance, but if you are trying to account for the exact ROI of a keyword or ensure accurate budgets for each campaign, the canonical match can start to pose major problems.

For instance, let’s say you’re trying to figure out your top 10 keywords in order to develop a sophisticated bidding strategy. You may have no idea which keyword is actually doing best, but according to your reports, it appears that the keywords have very different performance. To you, the words appear to have different statistics and you think they have different ROIs. To the Yahoo system, the words appear to be the same and the advertising platform shows results based on what it thinks is the higher quality keyword.

My advice is to have your Yahoo account representative “dedup” or “deduplicate” your entire keyword list before uploading it into your account.

Back when Yahoo used Overture as their advertising platform, the canonical match was considered a competitive advantage since it was a more sophisticated way of thinking about keyword mapping. Now, Yahoo is discretely tearing apart canonical mapping in order to make their system more like Google and MSN.

Here’s the most important part of this article: Watch out for your Yahoo account keyword volume! If you lose significant volume off of a keyword that was formerly driving impressions & clicks, it may be because Yahoo has unmapped keywords from its former canonical match. You may need to create a keyword expansion to gain your volume back. (And let’s keep our fingers crossed that advanced match is helping cover what could be lost volume).

Yahoo appears to be quietly implementing a fix before advertisers begin to notice the flaw in their Panama system. Let’s hope this blog posting doesn’t reach too many people for their sake.