How does a canonical work and is it necessary to also have a no index, follow tag in place?

[kbbseo]

Across our site, we have canonical tags in place for URLs that contain duplicate content and for URLs without a trailing slash since we are using URLs WITH a trailing slash for all URLs across our site. We also recently added a no index, follow tag to all non-canonical URLs since we noticed a high number of duplicate content URLs in Google Webmaster Tools.

The first part of my question is: How does a canonical work? Does the robot read the canonical and immediately go to the canonical URL or does it continue to read past the canonical tag and get to the no index, follow tag if there is one present?

The second part of my question is: Is it necessary to have both a canonical tag and no index, follow tag in place? Or should the canonical tag be sufficient to avoid duplicate content?

And lastly, if both a canonical tag and no index, follow tag are in place, should they be in a specific order? Canonical tag first then no index, follow tag second or no index, follow tag first then canonical tag second?

I would appreciate any insight you can give. Thank you!

[kbbseo]

Thank you for you responses and advice!

[RyanKent]

Very nice addition John.

[john4math]

Ryan, spot on as always.

One other thing, it sounds like some of the canonicals you're placing on pages would be better suited to 301 redirects, like correcting a URL for not having a trailing slash or not.  If you can avoid using canonicals and use 301 redirects instead, that's the preferred method for resolving duplicate content issues.  Canonicals are more for when there are parameters on the URLs, and you can't get away from serving the pages with those parameters.

[RyanKent]

How does a canonical work? Does the robot read the canonical and immediately go to the canonical URL or does it continue to read past the canonical tag and get to the no index, follow tag if there is one present?

The first thing to understand is the canonical tag is a suggestion, not an order. While a search engine will usually honor the canonical tag, there are instances where Google or other SEs may determine the canonical tag is not being used correctly so they disregard the canonical tag. Based on this understanding, yes the robot will read the entire page regardless of the canonical tag status.

Is it necessary to have both a canonical tag and no index, follow tag in place? Or should the canonical tag be sufficient to avoid duplicate content?

The two tags you mention conflict. You would never use both tags on the same page.

Noindex means you do not wish the page to appear in the search index. The canonical tag means you do wish the content to be included in the search index, but use the canonical URL in the index.

if both a canonical tag and no index, follow tag are in place, should they be in a specific order?

The order of meta tags does not matter. If a page was marked with both a canonical tag and a noindex tag, the noindex tag would take effect and the page would not be indexed, so the canonical tag would not have any effect.

In short, you want to use the canonical tag to resolve duplicate content issues, not the noindex tag.