Should I disallow all URL query strings/parameters in Robots.txt?

[jmorehouse]

Webmaster Tools correctly identifies the query strings/parameters used in my URLs, but still reports duplicate title tags and meta descriptions for the original URL and the versions with parameters. For example, Webmaster Tools would report duplicates for the following URLs, despite it correctly identifying the "cat_id" and "kw" parameters:

/Mulligan-Practitioner-CD-ROM
/Mulligan-Practitioner-CD-ROM?cat_id=87
/Mulligan-Practitioner-CD-ROM?kw=CROM

Additionally, theses pages have self-referential canonical tags, so I would think I'd be covered, but I recently read that another Mozzer saw a great improvement after disallowing all query/parameter URLs, despite Webmaster Tools not reporting any errors.

As I see it, I have two options:

1. Manually tell Google that these parameters have no effect on page content via the URL Parameters section in Webmaster Tools (in case Google is unable to automatically detect this, and I am being penalized as a result).
2. Add "Disallow: *?" to hide all query/parameter URLs from Google. My concern here is that most backlinks include the parameters, and in some cases these parameter URLs outrank the original.

Any thoughts?

[OlegKorneitchouk]

"I recently read that another Mozzer saw a great improvement after disallowing all query/parameter URLs" - do you have a link for this?

Canonicals should be enough but Google does mess up and the more clues you can give them, the better.

You can also manually tell Google parameter meanings (if you check out your parameter page now in search console, you should see all of the parameters they've detected for you - you can just change their meaning).

I don't see any harm in disallowing parameters via robots.txt. They will still be crawled and internal links followed, just not indexed in serps.

[PatrickDelehanty]

Hi there

I recently answered a question in a similar question in the Q+A that references resources that can help you help Google understand these parameters and categorize them. You can read that here.

That being said, blocking these parameters in your robots.txt will not affect your rankings, especially if those parameter or query strings are properly canonicalized to the proper product page.

That being said, I would make sure you understand the resources above and the options, as you understand your users and website better than anyone - test on a few pages to see what happens and go from there.

Hope this helps! Good luck!

[jmorehouse]

The statement was in a response to a question I asked earlier.

"I was having an issue like this where moz was showing a lot more duplicate content than webmaster tools was, actually webmaster tools showed none, but I was being penalized. I realized this when I added an exclusion to robots.txt to exclude any query strings on my site. After I did this I saw my rankings shoot through the roof."

Thanks for the info. I did edit the settings in the URL parameters section to tell Google that these parameters do not change the page content, so it should now index only one representative URL. My only concern was that the kw (keyword) parameter does change page content for search result pages, but I just read that Matt Cutts encourages disallowing those pages anyway.

Just to verify, disallowing those pages with parameters won't affect the "link juice" passed from external links?

[OlegKorneitchouk]

Correct. They won't be indexed but are still followed.