Understanding Duplicate Content
Paste two pieces of content and this tool measures how much they overlap, then gives a plain verdict: likely duplicate, significant overlap, or sufficiently unique. Everything runs in your browser, so unpublished pages stay private.
Duplicate content is one of the most misunderstood topics in SEO. There is no penalty for it in the way people imagine, but it does cause real problems — just different ones from the ones most articles describe.
There is no duplicate content penalty
Google has stated repeatedly that duplicate content does not trigger a penalty. Manual actions exist for deliberate, deceptive scraping at scale, but ordinary duplication — two similar product pages, a syndicated article, a printer-friendly version — is handled by filtering rather than punishment.
What actually happens is consolidation. When Google finds several URLs with substantially the same content, it picks one to show and filters the others out of results. Your page is not penalised; it is simply not the one chosen.
The real cost is dilution. Ranking signals that would have concentrated on one strong page get split across several weak ones, and the version Google picks may not be the one you would have chosen.
The three kinds of duplication
- Technical duplication — the same page reachable at several URLs through parameters, protocols or trailing slashes. Fixed with canonical tags, not by rewriting.
- Internal duplication — two genuinely different pages on your site that cover the same topic and intent. Usually fixed by merging and redirecting.
- External duplication — your content appearing on other sites, or supplier text you share with competitors. Fixed by writing something distinct.
Which type do you have?
This distinction determines the fix entirely, and getting it wrong wastes effort. If the same content is reachable at /product and /product?colour=blue, rewriting the text achieves nothing — the two URLs will still be duplicates of each other. That needs a canonical tag.
If you have two separate blog posts both targeting “how to clean running shoes”, no canonical will help, because they are genuinely different pages competing for one query. Merging them into one stronger page and redirecting the loser is the fix.
If your product descriptions are the manufacturer's supplied text, so are your competitors', and none of you has anything distinctive. That one does need writing.
Reading the verdict
The tool uses cosine similarity over word usage, which measures literal overlap. Above 80% it reports likely duplicate; 50–80% significant overlap; below that, sufficiently unique.
These thresholds are working guides rather than Google's. Google does not publish a similarity threshold and does not evaluate duplication this way — its systems assess meaning and context across the whole web, not word vectors between two pasted texts.
So a high score is a prompt to investigate, not a verdict. Two legitimately distinct pages on a narrow technical topic can score high simply because they need the same vocabulary. Read them and ask whether a searcher would be satisfied by either one.
When duplication is genuinely fine
Boilerplate is fine. Your footer, navigation, disclaimers and about-us blurb appearing on every page is normal and Google handles it without difficulty.
Quoting sources is fine, provided the quote is attributed and your page adds something around it. Syndication is fine when the republished copy carries a canonical pointing back to your original.
Regional variants are fine when marked up properly. Near-identical US and UK pages should carry hreflang tags so search engines treat them as alternates rather than duplicates.
Practical next steps
For a high score between two of your own pages, decide which should survive. Merge the useful content into it, redirect the other, and update internal links so nothing points at the retired URL — the Internal Link Analyzer shows what currently links where.
For duplication within a single document rather than between two, the Duplicate Sentence Finder and Duplicate Paragraph Finder catch repeated blocks — common in content assembled from several sources.
If you want to see exactly which passages overlap rather than a single score, the Text Diff Checker highlights every difference word by word.
Frequently asked questions
Does Google penalise duplicate content?
No. Google filters duplicates rather than penalising them — it picks one version to show and suppresses the others. Manual actions exist only for deliberate, deceptive scraping at scale, not for ordinary duplication.
What percentage counts as duplicate?
There is no official figure. This tool flags above 80% as likely duplicate as a working guide, but two legitimately distinct pages on a narrow topic can score high because they share necessary vocabulary. Use it as a prompt to look, not a verdict.
How do I fix duplicate content?
It depends on the type. Duplicate URLs need a canonical tag or redirect. Two competing pages need merging. Supplier or syndicated text needs rewriting. Applying the wrong fix wastes effort, so identify the type first.
Is boilerplate like footers a problem?
No. Navigation, footers, disclaimers and standard blurbs repeating across a site are entirely normal and Google handles them without issue. The concern is duplication of the main content.
Does it check against the whole web?
No. It compares only the two texts you paste, and everything runs in your browser with nothing uploaded — which is also why it cannot search for external copies of your content.