What is Canonical URL?

[jaysh4922]

Canonical Urls are on the page and define which url the page should be indexed as. This is used when you have one or more url parameters that might resolve that same content.

[oneyestech]

Rel canonical is a tag in the header of your HMTL that tells search engines which piece of content is the original and which one is a duplicate.

There are multiple situations where canonical should be used for duplicate content:

Multiple URLs: e-commerce websites which offer filter options like prices, sizes, colors, categories have a lot of URLs with duplicate content

HTTP, HTTPS, WWW: a search engine can see http://www.mywebsite.com, https://mywebsite.com and https://www.mywebsite.com as different websites and will index them as such

www.example.com
example.com
www.example.com/index.html
example.com/home.asp