How can URL parameters, like session IDs or tracking IDs, cause duplicate content?
When user and/or tracking information is stored through URL parameters, duplicate content can arise because the same page is accessible through numerous URLs. In the example below, URL parameters create three URLs which access the same product page.
Why should you care?
- Having multiple URLs can dilute link popularity. For example, in the diagram above, rather than 50 links to your intended display URL, the 50 links may be divided three ways among the three distinct URLs.
- Search results may display user-unfriendly URLs (long URLs with tracking IDs, session IDs)
If you find you have duplicate content as mentioned above, can you help search engines understand your site?
1. Removing unnecessary URL parameters — keep the URL as clean as possible.
2. Submitting a Sitemap with the canonical (i.e. representative) version of each URL.
How can you design your site to reduce duplicate content?
- When tracking visitor information, use 301 redirects to redirect URLs with parameters such as affiliateID, trackingID, etc. to the canonical version.
- Use a cookie to set the affiliateID and trackingID values.