The tool
What this Claude Copyleaks checker is
Start with what it is not. This is not Copyleaks, it does not run Copyleaks, and there is no affiliation of any kind between us. It cannot tell you what a Copyleaks scan will say about your text, and nothing on this page should be read as a prediction of one.
What it is: a text checker that reads what you paste and writes back findings about the writing itself. Patterns in the sentences, repetition, places where the prose flattens out. It runs on our server, so your text is sent to us, and the allowance is 5 free runs every rolling 24 hours with an input of 1 to 12,000 characters.
The comparison
What a Copyleaks scan returns, and what this returns
Copyleaks publishes its own API description, and it is worth reading before you decide what you want. Their detection returns "a per-section classification (human or AI)", an "overall human-versus-AI summary", and what they call AI Logic explanations of why content was flagged, including highlighting "specific sentences that sound like AI writing". They document support for "30+ languages".
This checker returns none of those things. There is no classification of any sentence or section, no overall verdict, no highlighting and no language count. You get written findings about observable qualities of the text and an explicit statement of what the reading cannot tell. If you want a span-level verdict, this is the wrong tool and we would rather say so than imitate one.
How it works
How to check your text in three steps
This is a drafting tool. Use it while you can still change the writing.
- Step 1
- Paste the passage you are unsure about. There is no minimum length, so a single paragraph is a valid run and often a more useful one.
- Step 2
- Add an instruction of up to 300 characters naming what you want examined, then press Analyze. Your text is sent to our server for the run.
- Step 3
- Read the findings against your draft and change what you agree with. Nothing here produces a number, so there is nothing to edit toward.
Why no score
A likelihood score is a setting, not a fact
A published review of the Copyleaks checker describes its output as "a likelihood score and sensitivity options", with "adjustable sensitivity settings" for different use cases. That is a reasonable product decision and it also tells you something important: if the verdict moves when a reviewer moves a control, the verdict is partly a policy choice about how much risk that institution wants to carry.
Text does not change when a slider does. That is the reason this checker produces sentences rather than a percentage. A finding like "the middle three paragraphs all open the same way" is either true of your draft or it is not, and you can verify it in about ten seconds without trusting us at all.
A common mix-up
The Copyleaks checker name, and plagiarism
Copyleaks sells two related products, plagiarism detection and AI detection, and the pages listing alternatives to it blur them constantly. Worth being clear: this route does neither in the sense those products mean.
There is no corpus here, no index of published work, no similarity matching and no source reporting. Nothing your text is compared against exists on this route at all. If you need a similarity report for a submission, you need a plagiarism service, and this is not one.
The real question
What to do if your work will be scanned
The honest answer is short. Improve the writing, because that is the only thing you control and the only thing that survives any scan. Keep the evidence of how the work was made: drafts, notes, version history, the sources you read. If your institution or client has an AI use policy, follow it and disclose under it rather than editing to move a result you cannot see.
What will not help is rewriting to beat a detector. You cannot see the output, we cannot see the output, and every careful page in this category concedes that edited text moves results unpredictably. You would be optimising against an invisible target and making your prose worse on the way.
Access
What free means on each side
The review we read puts the Copyleaks position plainly: "Copyleaks offers limited free access for testing. Full AI detection and plagiarism checking require a paid plan", and its pricing "may not suit occasional users" because the product is aimed at professional and organisational use. That is a fair description of a business-to-business tool.
Ours is smaller and simpler. 5 runs every rolling 24 hours, no account, no card, nothing stored, and no tier above the free one to be upsold into. When the runs are gone the tool tells you when the window resets.
Limits, stated
What this Copyleaks checker will not do
No Copyleaks result, no estimate of one and no relationship with Copyleaks. No percentage, no likelihood score, no sensitivity setting, no per-sentence or per-section labelling. No plagiarism matching, no source list, no similarity report.
No file upload, so a document has to be pasted as text into a box capped at 12,000 characters. No accuracy figure, because we have measured none and borrowing someone else's measurement would describe a different engine. No claim about who or what wrote your text, ever.