Lately, I have been running into some very complex technical issues. One that recently came up was, what does Google do if there are 2 rel canonicals on the same page, but they both point a different pages? After doing a little digging, I found the answer directly from Google.
2 rel canonical links different urls SEO
Here is a quote from Google,” Another issue is when pages include multiple rel=canonical links to different URLs. This happens frequently in conjunction with SEO plugins that often insert a default rel=canonical link, possibly unbeknownst to the webmaster who installed the plugin. In cases of multiple declarations of rel=canonical, Google will likely ignore all the rel=canonical hints. Any benefit that a legitimate rel=canonical might have offered will be lost.”
So what does this mean for SEO? Well, it means do not place 2 rel canonicals on the same page or Google will ignore them both, in most cases.