Because of the nature of my website I have duplicated content. For instance one jumper might be in my sweater section and my top selling section. This is obviosuly bad for SEO. I've learnt that I need to use rel=canonical tags to solve the problem, but how do I do this?
I also have a lot of repeated content in descriptions e.g. when listing the material composition of the clothing and washing instructions. I've learnt that to solve this problem I need to use robots.txt to block off these repetitive sections. But again, I don't know how to do this.
Thanks in advance for your advice :)
Britton here with the Shopify support team.
The canonical tags are really meant to be used when you have two different URLs on a site that lead to exactly the same page. These tags then let Google know which if the two identical pages is the one to serve. All of the themes currently on the Shopify theme store come with these necessary canonicalizations right out of the box, meaning that you don't need to take any actions on this.
As for the robots.txt file, it is not actually possible to edit that directly on Shopify. If you are really concerned about a link though, you can always use a "nofollow" in the actual link html. You can find some instructions on this here: https://support.google.com/webmasters/answer/96569?hl=en.
That being said, for normal content duplications like this there is not really too much cause to worry from an SEO perspective. Google has stated that the normal kinds of content duplication that occur from the honest and correct creation of websites is not something to worry about. They only penalize people who are being dishonest or abusive with their duplications. You can find a video published by Google where they discuss this topic in depth here: https://www.youtube.com/watch?v=mQZY7EmjbMA.
I hope this helps to put your concerns to rest!