In general I pretty much like the idea of canonicalization. And in most cases, Google explains possible procedures in a clear way.

For example: If I have duplicates because of parameters (eg: &sort=desc) it's clear to use the canonical for the site, provided the within the head-tag.

However I'm wondering how to handle "small - no to say thin content - sites". What's my definition of a small site? An Example: On one of my main sites, we use a directory based url-structure. Let's see:

• example.com/ (root)
• example.com/category-abc/
• example.com/category-abc/produkt-xy/

Moreover we provide on page, that includes all products

• example.com/all-categories/ (lists all products the same way as in the categories)

In case of reviews, we use a similar structure:

• example.com/reviews/product-xy/ shows all review for one certain product
• example.com/reviews/product-xy/abc-your-product-is-great/ shows one certain review
• example.com/reviews/ shows all reviews for all products (latest first)

Let's make it even more complicated: On every product site, there are the latest 2 reviews at the end of the page. So you see, a lot of potential duplicates.

Q1: Should I create canonicals for

• a: example.com/category-abc/ to example.com/all-categories/
• b: example.com/reviews/product-xy/abc-your-product-is-great/ to example.com/reviews/product-xy/ or to example.com/review/ or none of them?

Q2: Can I link the collection of categories (all-categories/) and collection of all reviews (reviews/ and reviews/product-xy/) to the single category respectively to the single review.

Example: example.com/reviews/ includes - let's say - 100 reviews. Can I somehow use a markup that tells search engines: "Hey, wait, you are now looking at a collection of 100 reviews - do not index this collection, you should rather prefer indexing every single review as a single page!".

In HTML it might be something like that (which - of course - does not work, it's only to show you what I mean):

<div class="review" 
rel="canonical" href="http://example.com/reviews/product-xz/abc-your-product-is-great/">
HERE GOES THE REVIEW</div>

Reason: I don't think it is a great user experience if the user searches for "your product is great" and lands on example.com/reviews/ instead of example.com/reviews/product-xy/abc-your-product-is-great/. On the first site, he will have to search and might stop because of frustration. The second result, however, might lead to a conversion.

The same applies for categories. If the user is searching for category-Z, he might land on the all-categories page and he has to scroll down to the (last) category, to find what he searched for (Z).

So what's best practice? What should I do?