Paste two pieces of text and instantly see how similar they are. The checker calculates a similarity percentage, breaks down word and phrase overlap, and highlights the exact passages the two texts share — so you can spot duplication, near-duplicate pages and unintended copying. 100% in your browser — nothing is uploaded or stored.
🔒 Everything runs in your browser. Your text is never uploaded, logged or stored.
The Duplicate Content Checker compares two pieces of text and tells you how similar they are, with a clear percentage score and the exact shared passages highlighted side by side. It is built for the moment you need to know whether two pages, two product descriptions, or a draft and its source overlap too much — before that duplication causes problems. Rather than guessing, it measures word and phrase overlap mathematically, shows you the longest run of words the two texts share, and marks every matching passage so you can rewrite with precision.
It is part of the SERP & Content Analysis group in our free SEO Toolkit. Pair it with the Word Count & Reading Time Analyzer to size each version, the Keyword Density Analyzer to compare term balance, the Text Readability Scorer to check clarity after rewriting, and the Meta Description Length Checker to keep each page's snippet unique. Everything runs in your browser — your text is never uploaded or stored.
A score, a breakdown, and the shared passages.
A clear percentage from word and phrase overlap.
Word overlap, phrase match, containment and longest shared run.
Shared passages marked in both texts, side by side.
All comparison happens in your browser — nothing leaves your device.
From two drafts to a clear overlap report.
Your first piece of content.
The text to compare it against.
Get the similarity score and metrics.
Edit the highlighted shared passages.
A guide to reading the percentage.
A duplicate content checker compares two pieces of text and measures how much they have in common. Instead of a vague impression that two pages feel alike, it gives you a similarity percentage, a breakdown of where the overlap comes from, and a visual map of the exact passages the texts share. This tool compares the two texts you paste against each other — it does not crawl the web — which makes it ideal for checking a draft against its source, comparing two product descriptions, or confirming that a rewrite is different enough from the original. It is part of the SERP & Content Analysis group in the SEO Toolkit.
Duplicate content rarely earns a penalty on its own, but it causes real problems. When several pages say nearly the same thing, search engines must choose one to show and may suppress the rest, splitting your ranking signals and wasting crawl budget. Near-duplicate product or location pages are a classic source of pages that get crawled but not indexed. And reusing text across your own site, or unintentionally echoing a source too closely, dilutes the originality that helps content stand out. Knowing precisely where two texts overlap lets you fix the problem at its root rather than guessing.
Similar pages compete with each other and dilute rankings.
Near-duplicates often end up crawled but not indexed.
Spot product or location pages that are barely different.
Confirm a rewrite is genuinely distinct from its source.
The headline similarity figure is a Jaccard score over three-word phrases, or shingles: the tool slides a three-word window across each text, builds the set of phrases for both, and reports the proportion shared out of the total unique phrases. This phrase-level approach catches genuine copying while ignoring the coincidence that two texts both use common words. Alongside it you get single-word overlap, a containment figure showing how much of Text A appears in Text B, and the longest unbroken run of words the two share — a strong signal of direct copying. Together these give a fuller picture than any single number.
The main score is a Jaccard similarity over three-word shingles. The tool lowercases and tokenises both texts, builds the set of every three-word phrase in each, then divides the number of shared phrases by the total number of unique phrases across both. The result is a robust phrase-level measure that ignores word order at the document level while still rewarding genuinely shared wording.
No, and that is deliberate. Scanning the live web requires a search index and server-side crawling, which a private in-browser tool cannot do. Instead this compares the two texts you provide against each other, which is exactly what you need for checking drafts, rewrites, and your own pages. For web-wide plagiarism scanning you would need a dedicated indexed service.
Short matches of one to three words happen naturally between any two texts on the same topic and would clutter the view with noise. Requiring a shared run of at least four consecutive words surfaces meaningful copied passages rather than coincidental overlaps, so the highlighting points you to the sections that actually need rewriting.
No. Tokenising, scoring and highlighting all run entirely in your browser with JavaScript, and the tool never makes a network request with your text. Nothing you paste is uploaded, logged or stored, so it is safe for unpublished drafts, confidential documents and client work.
Check that similar products have distinct descriptions.
Spot near-identical city or service pages before publishing.
Confirm a paraphrase is different enough from its source.
Compare your draft against quoted material for overlap.
Use the Duplicate Content Checker with these tools from the SEO Toolkit: size each version with the Word Count & Reading Time Analyzer, compare term balance with the Keyword Density Analyzer, check clarity after rewriting with the Text Readability Scorer, keep each page's snippet unique with the Meta Description Length Checker and Title Tag Length Checker, organise sections with the Heading Structure Checker, and audit a page's tags with the Meta Tag Analyzer.
Anyone who needs content to be original.
Everything about duplicate content checking.
It compares two pieces of text you paste and measures how similar they are, giving an overall similarity percentage, a breakdown of word and phrase overlap, the longest shared run of words, and a side-by-side highlight of every matching passage so you can see exactly where the two texts coincide.
Yes, completely. There is no cost, no sign-up and no limit on how many comparisons you run. The tool works entirely in your browser, so there are no server costs and nothing to pay for.
No. Scanning the live web needs a search index and server-side crawling, which a private in-browser tool cannot do. This tool compares the two texts you provide against each other, which is exactly what you need for checking drafts, rewrites and your own pages. Web-wide scanning requires a dedicated indexed service.
The main score is a Jaccard similarity over three-word phrases. The tool builds the set of every three-word phrase in each text, then divides the number of shared phrases by the total unique phrases across both. This phrase-level measure rewards genuine shared wording while ignoring the coincidence of common individual words.
As a rough guide, under 15 percent is largely unique, 15 to 40 percent shows some overlap worth reviewing, 40 to 70 percent indicates substantial shared content, and above 70 percent means the texts are likely near-duplicates. The right threshold depends on context — quoted material naturally raises the figure.
Matches of one to three words occur naturally between any two texts on the same topic and would fill the view with noise. Requiring a shared run of at least four consecutive words surfaces meaningful copied passages rather than coincidental overlaps, pointing you to the sections that genuinely need rewriting.
Usually not a direct penalty, but it causes practical problems: search engines pick one version to show and may suppress the others, splitting ranking signals and wasting crawl budget. Near-duplicate pages are a common reason for pages being crawled but not indexed, so reducing overlap helps your pages compete properly.
Yes, that is one of the most useful cases. Paste the text of two pages — for example two product or location pages — to see how much they share. The highlighting shows which passages to make distinct so each page targets its own audience instead of competing with its sibling.
No. Tokenising, scoring and highlighting all run entirely in your browser with JavaScript, and the tool never sends your text over the network. Nothing you paste is uploaded, logged or stored, so it is safe for unpublished drafts, confidential documents and client work.
Yes. Because the score is based on shared three-word phrases, changing words within a phrase breaks that phrase and lowers the similarity. This makes the tool a practical rewriting aid: edit the highlighted passages, run the comparison again, and watch the percentage fall as the texts become genuinely distinct.
Yes. The checker is fully responsive, so you can paste both texts and read the full report from a phone or tablet. The score card, the metrics and the side-by-side highlighted panels all display and scroll cleanly on small screens just as they do on desktop.
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Compare two texts, get a clear similarity score and detailed overlap metrics, and see every shared passage highlighted — free, private and instant in your browser.
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