There is an interesting response from John Mueller of Google on what to do with URLs that may appear duplicated because of URL parameters, like UTMs, at the end of the URLs. John said definitely don’t 404 those URLs, which I think no one would argue with. But he also said you can use the rel=canonical because that was what it was made for. The kicker is he said it probably doesn’t matter either way for SEO.

Now, I had to read John’s response a couple of times on Reddit and maybe I am interpreting the last part incorrectly, so help me out here.

Here is the question:

John’s 404 response:

John’s canonical response:

Okay, so far, do not use 404s in this situation but do use rel=canonical – got it.

John then explained SEO wise, it probably doesn’t matter?

So Google will likely handle the duplicate URLs, the UTM parameters anyway, even if they do index them. But to make SEO consultants happy, use the rel=canonical? Is that what he is saying here? I do like that response, if that is his message – but maybe I got it wrong?

Forum discussion at Reddit.