How to correctly specify the canonical address of the page?

Question

Search Engine Optimization

Hey!
I have an online store and now I am engaged in its SEO optimization.
This store has a catalog of goods https://site.ru/catalog
Tabulation is made using the GET page parameter, i.e. https://site.ru/catalog?page=1 , https://site.ru/catalog?page =2 etc.
The question is, how do I correctly specify the canonical address, and should I do it at all?
And the second question, is it necessary to specify the canonical address for the error page? For example, there was a product on the site that was indexed by search engines, but after some time the product was removed from sale and the link that led to this product now leads to a page with a 404 error, and there can be many such pages.

Answer 1

Tabulation is done using the page GET parameter, i.e. https://site.ru/catalog?page=1 , https://site.ru/catalog?page=2 , etc.

Why is she made like that?
Do you have all the goods in one pile? Are there no categories at all?
It used to be said that Google does not like catalog pages, now advanced shopkeepers say that, on the contrary, well-made pages with product categories are very favored by Google.

The question is, how do I correctly specify the canonical address, and should I do it at all?

The canonical address is needed when the same page can be reached by several URLs - you give the search engine a hint about which URL is the main ("main").
If you have ?page=1, ?page=2, etc. the same thing, then yes - you need to select the main page. If not, then indicate so, do not forget about all kinds of sorting - by price, by popularity, etc., they need to be worked out, like other parameters that may appear in the URL.

and the site had a product that was indexed by search engines, but after some time the product was removed from sale and the link that led to this product now leads to a page with a 404 error

Why is she taking it there?
Save the product page, indicate "out of stock" (possibly add information about the prospects for availability), and display suggestions for "notify when available" as well as alternatives to this product that are in stock.

Answer 2

The canonical is indicated if you have 2 addresses with the same content, for example, a product can be found by article or nc, then the link with a non-permanent identifier (nc) indicates a canonical url with a digital permanent identifier.