by The Computing Australia Group | What is Duplicate
Content?
Duplicate content is one of those SEO problems that often flies under the radar—until rankings slip, pages stop performing, or Google indexes a version of a URL you never intended anyone to see. At its simplest, duplicate content is content that is the same (or very similar) across multiple URLs. It can exist within the same website (internal duplication) or across different websites (external duplication).
Despite the common myth, Google doesn’t “hate” duplicate content in the sense of automatically penalising every site that has it. What Google does struggle with is deciding which version of a page should be indexed and ranked, how link equity should be distributed, and which URL should appear in search results. That uncertainty can lead to lower visibility, diluted authority, and missed opportunities—especially for competitive queries.
In this expanded guide, we’ll break down:
- The real SEO issues duplicate content causes
- The most common technical and content-related causes
- E-commerce and CMS duplication traps
- A practical, step-by-step fix list (with examples)
- Ongoing prevention strategies so the problem doesn’t return
What is Duplicate Content?
Duplicate content refers to blocks of content that are either:
- Exactly the same, or
- Substantially similar,
…and are accessible at more than one URL.
Examples:
- The same product page being reachable via multiple URL parameter variations
- A blog post accessible via HTTP and HTTPS
- A printer-friendly page indexed alongside the original
- A copied article posted elsewhere without proper attribution or canonicalisation
Duplicate content becomes an SEO issue when search engines can’t confidently determine:
- Which version is the “main” version
- Which version should rank
- Where links and authority should be consolidated
Why Duplicate Content Causes SEO Problems
1) Search engines can’t decide which version to rank
That can translate into unstable rankings and missed traffic.
- Rank the “wrong” URL
- Rotate which URL shows up over time
- Choose not to rank either strongly
If two or more URLs contain the same (or near-identical) content, Google may:
2) Index bloat and wasted crawl budget
- E-commerce stores with filters and sorting
- Large blogs with multiple archives/tags
- Sites with parameter-heavy URLs
Search engines allocate limited crawling resources to your site. If Googlebot spends time crawling duplicate URLs, it may crawl important pages less frequently—slowing indexing and reducing performance for your best content.
This is especially relevant for:
3) Link equity gets diluted
When other websites link to your content, ideally all backlinks point to one canonical URL. With duplicates, links may spread across multiple versions, such as:
- /product and /product/
- https://www.example.com/page and https://example.com/page
- ?source=rss vs no parameter
Instead of one strong page, you end up with several weaker versions.
4) Internal signals become inconsistent
Duplicate content can also confuse your own internal linking structure. If your navigation and templates generate different URL forms across the site, Google receives mixed signals about which version is preferred.
Common Causes of Duplicate Content
WWW vs non-WWW and HTTP vs HTTPS
This is one of the most common causes: multiple accessible versions of the same site, like:
- http://example.com
- http://www.example.com
- https://example.com
- https://www.example.com
If all versions load without redirecting to one preferred version, every page can be duplicated across variants.
What to do:Choose one primary version (usually https://www) and enforce it with sitewide 301 redirects, plus consistent internal links and canonical tags.
Trailing slashes, uppercase URLs, and index pages
These are easy to miss but can create duplication:
- /services vs /services/
- /About vs /about
- /page vs /page/index.html
Some servers treat these as different URLs. Even if they look the same to users, search engines can index both.
What to do:
- Standardise URL formatting sitewide
- Use redirects from non-preferred versions to preferred versions
- Ensure internal links always use the preferred format
Session IDs
Many online stores and web apps track a visitor’s session using cookies. However, when cookies aren’t available or aren’t relied upon, some systems append a Session ID to the URL, creating something like:
- /category/shoes?sessionid=ABC123
Because Session IDs are unique, search engines may discover endless URL variants—each appearing to be a “new page,” even though the content is the same.
Why it’s a problem:
- Thousands of duplicate URLs
- Crawl budget waste
- Index bloat
- Avoid URL-based sessions for SEO-critical pages
- Prefer cookie-based sessions
- Block session parameters in robots.txt carefully (robots.txt prevents crawling, not indexing, if URLs are discovered elsewhere)
- Use canonical tags that point to the clean URL
- Configure parameter handling in Google Search Console (where applicable)
Order of URL parameters
Some CMS platforms generate URLs where parameter order changes, like:
- /?P1=1&P2=2
- /?P2=2&P1=1
Even if these load the same content, search engines often treat them as different URLs.
What to do:
- Implement canonical URLs to the clean, preferred version
- Use server-side rules to normalise parameter order (when feasible)
- Where parameters don’t change content meaningfully, consider stripping them via redirects
Tracking parameters and URL variables
Tracking is essential for marketing—but it often creates duplicate URLs:
- https://www.example.com/product-1
- https://www.example.com/product-1?source=rss
- https://www.example.com/product-1?utm_source=newsletter&utm_medium=email
From a user’s perspective these are the same page; from a search engine’s perspective, they can be separate URLs.
What to do:
- Ensure canonical tags point to the non-parameter version
- Keep internal links clean (don’t link internally with tracking parameters)
- Consider server-side redirects for specific parameters that shouldn’t be indexed
- Use consistent campaign tagging only on external ads/email, not internal navigation
Faceted navigation and filtered category pages
E-commerce sites are especially vulnerable. Filters like size, colour, brand, price, sorting, and “in stock” often generate parameter-based URLs:
- /shoes?colour=black&size=10&sort=price_asc
This can produce an enormous number of near-duplicate pages.
What to do:
- Decide which filter combinations deserve indexation (if any)
- Use canonical tags to the base category or to a curated indexable subset
- Use noindex, follow for thin filter pages (depending on strategy)
- Keep crawl paths under control (limit infinite combinations)
Printer-friendly pages
Many CMS platforms generate printer-friendly versions, such as:
- /article/how-to-choose-a-laptop
- /article/how-to-choose-a-laptop?print=1
If both versions are indexable, Google may index both.
What to do:
- Canonicalise print pages to the original
- Or noindex print versions
- Or block generation/indexing of print URLs entirely
Pagination and comment pagination
Pagination itself isn’t “bad,” but it can create duplication if not handled thoughtfully, especially with comment pages:
- /blog/post-title/
- /blog/post-title/comment-page-1/
- /blog/post-title/comment-page-2/
Sometimes each page repeats large chunks of the same article content.
What to do:
- Use canonical on comment pages (often pointing to the main post URL)
- Consider noindexing comment pagination if it offers little unique value
- For category pagination (/category/page/2/), a common approach is to allow indexation if pages are unique and useful, but ensure titles/meta are not duplicated
Scraped, syndicated, or copied content
Sometimes duplicate content comes from outside your website:
- Another site republishes your article without permission
- Content is scraped automatically
- Product descriptions are copied across many retailers
- Partner syndication posts identical text across multiple domains
What to do:
- Ensure your original page is strong, indexed, and has clear publication signals
- Use canonical tags properly on syndicated content (where you control both sides)
- Request attribution and canonicalisation from republishers
- If content is stolen, consider DMCA/takedown pathways (where appropriate)
Product descriptions and e-commerce duplication
Many online shops use the manufacturer’s default description. When dozens of stores use the same paragraph, it becomes extremely hard to rank.
What to do:
- Write unique product copy focusing on benefits, use cases, FAQs, specs, and comparisons
- Add original media (photos, videos, charts)
- Include unique elements like reviews, Q&A, size guides, and real-world examples
- Create category copy that differentiates your store (shipping, warranty, expertise)
Staging sites and development environments
A staging site that’s publicly accessible can cause a major duplication issue:
- staging.example.com indexed with the same content as the live site
- Or an old domain still live and crawlable
What to do:
- Password-protect staging environments
- Use noindex on staging + block crawling
- Ensure only one version is publicly accessible and indexable
How to Identify Duplicate Content
Here are practical ways to detect duplication (without drowning in tools):
- Google Search Console
- Look for indexing issues like “Duplicate, Google chose different canonical than user”
- Check “Page indexing” reports for duplicates and alternates
- Site query checks
- Search Google for site:example.com "unique sentence from your page"
- If multiple URLs show, you likely have duplicates
- Crawl your site
- Use a crawler to find duplicate titles, meta descriptions, and identical body text
- Log or analytics review
- If you see multiple URL variants receiving traffic for the same content, it’s a red flag
How to Fix Duplicate Content
1) Pick a preferred URL format and enforce it
Standardise:
- HTTPS (always)
- WWW or non-WWW (choose one)
- Trailing slash rules
- Lowercase URLs (where possible)
Then implement sitewide 301 redirects to enforce your preferred structure.
2) Use canonical tags correctly
Canonical tags tell search engines which URL is the “main” version.
Example: If parameters exist, canonical should point to the clean URL:
- Preferred: https://www.example.com/product-1
- Parameter: https://www.example.com/product-1?source=rss
Canonical should reference the preferred URL.
Best practices:
- Canonical should be absolute (full URL)
- Canonical should be self-referencing on the preferred page
- Canonical should not point to a URL that is blocked, redirected, or 404
3) Use 301 redirects when consolidation is clear
If an alternate URL should never exist publicly (e.g., HTTP pages, non-WWW variant, uppercase version), a redirect is usually better than canonical alone.
4) Control URL parameters (tracking and filters)
- Keep internal links clean
- Use canonicals to the clean page
- Consider noindex for thin filter pages
- Where possible, avoid generating crawlable links for infinite filter combinations
5) Improve uniqueness where it matters most
For product and service pages:
- Add original copy: benefits, differentiation, warranty, delivery info
- Add FAQs and comparisons (high intent)
- Add unique imagery/video
- Add structured data (schema) so Google understands the page better
6) Handle scraped content and syndication strategically
- If you syndicate your own content elsewhere, ask partners to:
- Add a canonical pointing to your original, or
- Use excerpts with a link back to the original
- For stolen content:
- Document evidence (timestamps, URLs)
- Request removal or attribution
- Escalate if necessary
Best Practices to Prevent Duplicate Content
- Keep a single source of truth for each page
- Ensure CMS settings are consistent (URL structure, trailing slash, archives)
- Audit new templates and plugins for parameter generation
- Regularly check Search Console for canonical/duplicate warnings
- Train content teams to avoid publishing near-identical pages targeting the same keywords
Duplicate content is fixable, but the right fix depends on your CMS, your site structure, and what you actually want Google to index. If you’d like an expert review and a practical action plan, contact our SEO pros in Perth at sales@computingaustralia.group. We can help you consolidate ranking signals, clean up indexation, and build a stronger foundation for long-term search growth.
Jargon Buster
Content Management System – CMS is the software used to create and manage digital content.
HTTPS – Hypertext Transfer Protocol Secure – An extension of the Hypertext Transfer Protocol used for protected communication over the internet.
Universal Resource Locator – URL – The web address of a specific page or file on the internet. It includes the protocol, the domain name, and additional path information.
Session ID – A unique number assigned to a specific user by the site’s server for the duration of that user’s visit. You can store it as a cookie, URL or form field.
Cookies – Text files containing small pieces of identification data sent by the server to your browser when you visit a website.
FAQ
Does Google penalise duplicate content?
Not automatically. The bigger issue is that Google may choose the wrong URL, split ranking signals, and reduce visibility. That looks like a penalty but is usually a consolidation/ranking issue.
Is duplication across product variants always bad?
Not always. Variant pages can be useful if they have unique value (e.g., distinct content, availability, reviews). If they’re nearly identical, consider consolidating under one canonical product page.
Should I block duplicate pages in robots.txt?
Be careful. Blocking crawling doesn’t always prevent indexing if Google finds the URL elsewhere. Canonicals, redirects, and noindex are often better solutions.
Can duplicate content come from “similar” pages, not exact copies?
Yes. Pages don’t need to be identical to cause issues. If two pages are substantially similar (same structure, same key paragraphs, only minor wording changes), Google may treat them as duplicates or near-duplicates and struggle to choose which one to rank. This often happens with location/service pages that reuse the same template, or product variant pages with only small spec changes.
Should I use noindex or canonical tags—what’s better?
It depends on your goal:
Use a canonical tag when you want the duplicate page accessible to users (e.g., tracking URLs, some filtered pages), but you want Google to consolidate ranking signals to the main URL.
Use noindex, follow when the page provides little or no search value (thin filter pages, printer pages, internal search results), but you still want links on that page to be crawled and pass equity.
In general, redirect when the duplicate URL should not exist, canonical when it can exist but shouldn’t rank separately, and noindex when it’s not meant to appear in search at all.
