There seems to conflicting information on how best to handle internal search results pages.
To recap - they are problematic because these pages generally result in lots of query parameters being appended to the URL string for every kind of search - whilst the title, meta-description and general framework of the page remain the same - which is flagged in Moz Pro Site Crawl - as duplicate, meta descriptions/h1s etc.
The general advice these days is NOT to disallow these pages in robots.txt anymore - because there is still value in their being crawled for all the links that appear on the page. But in order to handle the duplicate issues - the advice varies into two camps on what to do:
1. Add meta robots tag - with "noindex,follow" to the page
This means the page will not be indexed with all it's myriad queries and parameters. And so takes care of any duplicate meta /markup issues - but any other links from the page can still be crawled and indexed = better crawling, indexing of the site, however you lose any value the page itself might bring.
This is the advice Yoast recommends in 2017 : https://yoast.com/blocking-your-sites-search-results/ - who are adamant that Google just doesn't like or want to serve this kind of page anyway...
2. Just add a canonical link tag - this will ensure that the search results page is still indexed as well.
All the different query string URLs, and the array of results they serve - are 'canonicalised' as the same.
However - this seems a bit duplicitous as the results in the page body could all be very different. Also - all the paginated results pages - would be 'canonicalised' to the main search page - which we know Google states is not correct implementation of canonical tag
https://webmasters.googleblog.com/2013/04/5-common-mistakes-with-relcanonical.html
this picks up on this older discussion here from 2012
https://moz.com/community/q/internal-search-rel-canonical-vs-noindex-vs-robots-txt
Where the advice was leaning towards using canonicals because the user was seeing a percentage of inbound into these search result pages - but i wonder if it will still be the case ?
As the older discussion is now 6 years old - just wondering if there is any new approach or how others have chosen to handle internal search
I think a lot of the same issues occur with faceted navigation as discussed here in 2017
https://moz.com/blog/large-site-seo-basics-faceted-navigation
