Duplicate URLs
Last updated 17 June 2026 3 min
Duplicate URLs occur when two or more different URLs serve the same (or substantially the same) content. The page itself isn't necessarily duplicated — it's the addresses that create duplication in the eyes of search engines. This is one of the most common technical SEO problems on websites driven by CMSs like WordPress, and often exists without anyone noticing.
How duplicate URLs are created
Protocol and host variants
The same page can be reached via:
http://example.com/pagehttps://example.com/pagehttp://www.example.com/pagehttps://www.example.com/page
In the eyes of Google and other search engines, these are four distinct URLs.
Trailing slashes
/about/about/
Again, most search engines treat these as two different URLs.
URL parameters
/products/blue-mug/products/blue-mug?utm_source=newsletter/products/blue-mug?ref=homepage/products/blue-mug?sort=price&color=blue
Tracking parameters, session IDs, sort orders, and filters all generate URL variants pointing to identical or near-identical content that, again, are treated as distinct URLs.
Capitalisation
/Products/products
Some servers (especially Apache on Linux) treat these as different URLs, while Windows/IIS is case-insensitive by default.
Index file exposure
/folder//folder/index.html/folder/index.php
Print and AMP versions
/article/article?print=1/amp/article
Pagination and faceting
E-commerce category pages (Related: Pagination) with filters (?color=red&size=m) can produce thousands of low-value variants.
Why duplicate URLs matter
Diluted ranking signals
Links and engagement signals split across multiple URL variants instead of consolidating to one canonical version. The primary page for ranking is artificially weakened as a result.
Crawl budget waste
Search engines spend time crawling duplicates instead of new or updated content. For large sites, this can delay the indexing of new pages.
The wrong URL ranks
Google may pick the wrong variant to display in search — say, the http:// version, or the URL with a tracking parameter — leading to broken analytics attribution and poor user experience.
How to resolve duplicate URLs
301 redirects
The strongest signal. Use to consolidate:
- HTTP → HTTPS
- non-www → www (or vice versa)
- Trailing slash inconsistencies
- Old URL structures after migration
In the case of www vs non-www, neither is inherently "better". The point is to use one or the other consistently. The same is true for trailing slashes.
HTTPS should always be used over HTTP, as this has been a direct ranking signal for search engines for many years.
Canonical tags
When multiple URLs must remain accessible but only one should be indexed (e.g., parameterised filter pages, session IDs), canonical tags should be used to point these to the primary page.
Consistent internal linking
Always link to the canonical version internally. Mixed internal links (some to /about, some to /about/) dilute signals or create unnecessary redirects.
Sitemap hygiene
Only include canonical URLs in sitemaps. Duplicates or non-canonical URLs in the sitemap send conflicting signals.
Disclaimer: All information contained herein is for informational purposes only. It is not advice or instructional.