Using URL Parameters setting in Google Webmaster Tools to exclude temporary parameters

Question

I'm checking out the URL Parameters Google Webmaster Tools to exclude certain URL parameters, but I have to be careful according to Google.

So here's my question:

Through this URL:

www.example.com/products

, a user can view all products on my site. When a user views all products on my site in a certain area, it would look like this:

www.example.com/products/chicago

But if a user searches on a location where no results are returned, e.g. on "london", I redirect the user to:

www.example.com/products?all=1

Where I use that temporary all=1 parameter to show a messsage "no products found, we're now showing all products".

Parameter all only exists in the case no products are found and can only contain a value of 1 and no other value. I think it's safe to configure in Webmaster Tools that parameter "all" does not affect page content. I think in doing so, all URL's containing the parameter all=1 will be ignored, but the original URL, in the above scenario www.example.com/products, will still be indexed and shown. Is that correct?

Answer 1

I think it's safe to configure in Webmaster Tools that parameter "all" does not affect page content. I think in doing so, all URL's containing the parameter all=1 will be ignored

But Google's notification that follows appears to suggest otherwise:

... If many URLs differ only in this parameter, Googlebot will crawl one representative URL.

However, selecting "Yes" > "Other" > "No URLs". For which Google states: "Googlebot won't crawl any URLs containing this parameter." - would seem to be the desired result.

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An alternative to using Google's URL parameters (which, after all, only affects Google) is to simply set the appropriate rel="canonical" element for the page. ie. http://www.example.com/products. This would be the preferred option.