Why is Moz report showing duplicate content?

[BoomDialogue69]

Dear Moz Community

Our weekly Moz crawl diagnostic repoart is showing a significant increase in "Duplicate Page Content" errors for article pages that have unique content, unique file names, unique META title/descriptions, and unique H1 tags.

Where could the duplication be coming from?

Thanks for your help.

[Red_educativa]

I've understood where the problem was..

It was not a content problem, but something related with a "modal" we have put a couple of weeks ago...Thanks anyway!

Now I have everything under control

Greetings

Francesca

[BoomDialogue69]

Hi Francesca,

Thanks for posting a reply.

Regards,

Boom!

[Red_educativa]

Hi there...

I have the same problem, since 24Th of August 2013 I have around 2000/5000 errors (it depends on subdomains...) of duplicate page content...for this reason, I am taking advantage of this question..

The MOZ Crawler says (I put just one example)

http://es.tiching.com/clasificacion-de-los-seres-inertes/recurso-educativo/35632

has similar/identical content to

http://es.tiching.com/primaria/tercero/medio-natural-y-social/sc/195

But, have jut put both on "Similar page Checker" and the result is: ** 9% percentage similar**

http://www.webconfs.com/similar-page-checker.php

I guess this percentage is normal since the second one is a results page, instead the first one is just 1 content....

I have many like that but I really did not understand why, moreover I put canonical tag, both to the same page.

A >>> canonical >> A

B >>> canonical >>> B

Tks for helping and have a great day!!!

Francesca

[JoelDay]

Hey Justin,

Thanks for the question. How we determine duplicate content is if two or more pages have a 95% or greater overlap on the code level.

The example you provided has a ~97% overlap. Here's a handy tool for checking these: http://www.webconfs.com/similar-page-checker.php

As far as canonical tags, that's a bit of a hairy issue. Here's how we look at canonicals:

Assuming A, B, C, and D are all duplicates,

If A references B as the canonical, then they are not considered duplicates
If A and B both reference C as canonical, A and B are not considered duplicates of each other
If A references C as a canonical, A and B are considered duplicated
If A references C as canonical, B references D, then A and B are considered duplicates

I hope that helps. 
Cheers,
Joel.

[PaddyDisplays]

If the page is something like 90% the same then you will get a dupe error warning

Also moz report does not take into account canonical urls

[BoomDialogue69]

Great. We looked at the pages but the duplicate content isn't obvious....

[PaddyDisplays]

The report will let you what pages that its is a dupe with (where it says "Other URLs" click on the number)

[BoomDialogue69]

An example of this is:

http://www.sportsdirectnews.com/premier-league/26348-tottenham-transfer-news-spurs-interest-in-barry.php

and

http://www.sportsdirectnews.com/premier-league/20956-we-had-character-martinez.php