Do search engines crawl links with query strings?

Question

If I were to have a url like https://example.com/books, that contained several links to urls such as:

https://example.com/books?id=foo

https://example.com/books?id=bar

https://example.com/books?id=baz

Would search engines crawl and index the content returned by these URLs? If not, what would happen if I were to use a rewrite rule in my .htaccess file to rewrite pretty urls to ugly ones with query strings:

https://example.com/books/foo -> https://example.com/books?id=foo

https://example.com/books/bar -> https://example.com/books?id=bar

https://example.com/books/baz -> https://example.com/books?id=baz

Would there be any difference/preference? Or would a search engine crawl both?

Answer 1

Yes. Query strings are part of the URL and as such are viewed as directing the robots to different pages.

There may be a preference to using a path because then Google can test the parent. So if you have:

https://example.com/books/baz

Google will eventually test

https://example.com/books

on its own (it could be that they don't do it anymore though, but I'm sure I read that somewhere on a page owned by Google.)

One thing for sure, if you allow both, make sure to add a canonical meta tag with your preferred URL otherwise you could get penalized because of the duplication.