I'm building an eCommerce website which has an advanced filter on the left hand side of the category pages. It allows users to tick boxes for colours, sizes, materials, and so on. When they've made their choices they submit (this will likely be an AJAX thing in a future release, but isn't at time of writing). The new filtered page has a new URL, which is made up of the IDs of the filter's they've ticked - it's a bit like /department/2/17-7-4/10/ My concern is that the filtered pages are, on the most part, going to be the same as the parent. Which may lead to duplicate content. My other concern is that these two URLs would lead to the exact same page (although the system would never generate the 'wrong' URL) /department/2/17-7-4/10/ /department/2/**10/**17-7-4/ But I can't think of a way of canonicalising that automatically. Tricky. So the meat of the question is this: should I worry about this causing issues with the SEO - or can I have trust in Google to work it out?