Let's say there's a site with products. Each page product links to a page with a form to ask for more information. Let's say that URL is like:
XXX is the product code. So there are thousand of pages apparently with same 'content' (just a form, about 8 fields and a submit button).
Internally, the XXX is included in the form so I know what product the users wants info. But search engines detect this as duplicated content (because the form is the same).
How can I make clear the pages are different?
About canonical URLs
Usually, you have to provide a canonical URL in those case, to point the most important page of a group of duplicated pages. But in this case there's no point because all are equally important. Because of this, pages have a canonical URL metatag with a self-reference.
The only option I see is to include the product name in the title page and form header, so they are slightly different. Additionally, they may appear on search results when a user search for that product.
Is there any better approach?
If you have a single page accessible by multiple URLs, or different pages with similar content (for example, a page with both a mobile and a desktop version), Google sees these as duplicate versions of the same page. Google will choose one URL as the canonical version and crawl that, and all other URLs will be considered duplicate URLs and crawled less often. Therefor generally Google doesn't work with forms' items names but the contents.