Find matching passages
See which parts of your text match published content. Highlights help you focus on the wording that needs attention.
Free plagiarism checker
Our plagiarism checker finds matching passages and original sources. Review highlights, citations, and your similarity score.
Highlighted
text matches
Source links
review each match
3 free checks
to get started
characters (min 200): 0/500000
PDF, DOCX, TXT
See exactly where your text matches
Highlighted passages. Linked sources. A clearer next step.
A plagiarism detector that shows you the sources
Review original sources
Follow source links and compare the text in context. Decide whether to add a citation, quote a passage, or revise your draft.
Understand your score
See how much of your text matches available sources. Use the percentage as a starting point, then review the passages behind it.
How to check plagiarism
Use the plagiarism checker online to review a draft before you submit or publish it.
- 01
Paste or upload your text
Add your draft or upload a PDF, DOCX, or TXT document. Plagiarism is already selected — just run your scan.
- 02
Explore the matches
Review highlighted passages alongside their sources. Create an account to see full source details.
- 03
Check your citations
Add missing references, mark direct quotations, and revise where needed before you submit or publish.
For the work you write. And the work you review.
Plagiarism checker for students
Check your essay for plagiarism before you submit it. Review matching passages, check quotations, and find places where a reference may be missing.
Explore tools for studentsSupport thoughtful feedback
A plagiarism checker for teachers helps identify passages that deserve a closer look. Open the sources and discuss attribution with students in context.
Explore tools for teachersReview before you publish
Use a plagiarism checker for writers to review articles, blog posts, and client drafts. Find overlapping wording and verify attribution before publication.
Explore tools for writersPlagiarism vs AI detection
Two checks. Two different questions about your text.
| What you want to know | Plagiarism checking | AI detection |
|---|---|---|
| The question | Does this text match existing sources? | Does this text show signs of AI generation? |
| The result | Matching passages, source links, and a similarity score. | An estimate of AI-generated content. |
| What to review | Quotations, attribution, and context. | The writing process and supporting context. |
| The limit | Unmatched text is not proof of originality. | An AI score is not proof of plagiarism. |
Looking for an AI plagiarism checker? Start with the question you need to answer. Plagiarism checking finds source matches; AI detection assesses signs of AI-generated writing. You can use both in It's AI.
For developers & teams
Plagiarism Checker API
Bring source checking into your publishing platform, learning tools, or content review workflow. Send text to It's AI and get structured results your app can use.
View API docsAPI access is included with Enterprise.
POST
/api/v2/plagiarism/textOne check. Results you can build on.
- Similarity score
See how much of the text matches sources.
- Sources & matching passages
Get source URLs and compare both fragments.
- PDF report
Download a report for review or sharing.
Ensure originality of your work
Detect AI
Find plagiarism
Improve texts
Plagiarism checker FAQ
A few more questions?
What is a plagiarism checker?
A plagiarism checker compares your text with available sources to identify matching passages. It's AI shows highlighted matches, source links, and a similarity score to help you review attribution and context.
Is this plagiarism checker free?
Yes. The free plan includes 3 plagiarism checks, subject to your account’s word and text limits. Create an account to view full source details. Your account shows your remaining allowance; additional usage depends on your plan.
Can an AI plagiarism checker detect paraphrased AI text?
People often use “AI plagiarism checker” to describe two different tools. A plagiarism scan looks for wording that matches an existing source, but it can miss substantial paraphrasing and cannot establish whether AI wrote the text. AI detection addresses that separate question.
What does the similarity percentage mean?
It summarizes the portions of your text matched to sources by the checker. Properly cited quotations and common phrases may also match. A high score needs context, and a score of zero does not guarantee originality. Review the passages behind the percentage.
Can I check an essay or a document?
Yes. Paste your essay into the editor or upload a PDF, DOCX, or TXT document. Check the limits shown for your account before starting. For academic work, review the results alongside your institution’s citation requirements.
Does it check every academic database?
The checker looks for matching online sources. It does not guarantee access to every academic database or your university’s private submissions, and does not replace an institution’s required checking process.
Is plagiarism checking the same as AI detection?
No. Human-written text can copy a source, while AI-generated text may have no matching passages. Plagiarism checking finds source matches; AI detection estimates whether text may be AI-generated. Each answers a different question.
Does It’s AI offer a plagiarism checker API?
Yes. Our plagiarism checker API accepts text and returns a similarity score, source links, and matching passages. You can also retrieve a PDF report. API access is included with the Enterprise plan. See the documentation for authentication, usage limits, and examples. View API docs