A very common technique in ecommerce, is for products to be assigned a single category – part of the filing cabinet approach to site development. This works for niche ecommerce stores, but not for the majority. For example, a tshirt might belong equally in the following categories:’ red tshirts’, ‘logo tshirts’, ‘mens tshirts’ etc. Additionally there are times when it makes sense to have a multiple categories for a product and can help with conversions(a totally different topic).
The special care of multiple categories and SEO is that category pages contain a huge amount keyword rich anchor text. Yes, the majority of ecommerce software and system will allow filtering of results, but the canonical url tag is often used and results in messy links that are not ignored by search engines.
The major issue here is duplicate content – frowned upon by Google and can cause real issues for your site. Yes, a small numbers of pages is within acceptable limits, but when you have store that has hundreds of products duplicate content really can become an issue.
Using our tshirt example from above, say we place a product called ‘super baggy tshirt’ into the ‘red tshirts’ and ‘logo tshirts’ categories – the following two urls would be produced by our ecommerce software – the below structure is very common):
At first glance, this all looks well: SEO friendly URLs, well structured, organised and keyword rich. All this correct, apart from the fact that both URLs represent the same product – here is our duplicate content issue. The duplicate content issue will get worse if the product is placed into more categories. The easiest solution is to rewrite our product URL to something much simpler:
This will allow us to place the product into as many categories as we need without creating any duplicate content at all – there will always be a single version of the product URL.