The short answer
To check for plagiarism, run your finished draft through a plagiarism checker, read each match it finds, and decide what that match needs: quotation marks, a citation, a rewrite, or nothing. Then check the draft again.
The method has three parts:
- A tool check. It compares your text with sources and shows you where the wording matches.
- Your own reading. The tool finds matches. You decide whether each one is a problem.
- A few manual checks. They cover things a tool cannot see, such as a citation with no reference.
What a plagiarism check actually does
A plagiarism checker compares your text with sources it can search, such as web pages and published work, and shows the passages where your wording is the same as, or close to, a source.
It tells you two things:
- Which sentences match. These are highlighted in your text.
- What they match. A good report links the source for each match so you can compare the two.
It does not judge whether a match is cited. A quotation with quotation marks and a full citation is still matching text, so it is still highlighted. The checker also does not know whether a match was deliberate. Those calls are yours, and later your instructor’s or editor’s.
That is why “the checker found something” and “this is plagiarism” are different statements. For what does count, see what is plagiarism?
How to check your work, step by step
- Finish the draft first. Check a complete draft, with your quotations, citations and reference list in place. A half-written draft gives a report you will have to redo.
- Run it through a checker. Paste the text or upload the file. Include the whole paper, not only the parts you are worried about.
- Open the full report. Skip past the percentage and go to the highlighted sentences.
- Read each match next to its source. Ask where the wording came from and whether your paper says so.
- Decide what each match needs. The table in the next section covers the usual cases.
- Check again. Rewriting can introduce new matches, and a second check confirms the fixes worked.
Leave yourself time. A check an hour before the deadline can show you a problem you have no time to fix properly.
What to do with each match
Every match falls into one of a few situations. Go through them one at a time.
| What the match is | What to do |
|---|---|
| The exact words of a source, and you want to keep them | Quote it. Put the words in quotation marks and add a citation. |
| An idea or fact from a source, in your own words, with no citation | Cite it. The wording is yours but the idea is not. |
| A sentence that follows the source too closely | Rewrite it in your own words and structure, and still cite the source. |
| A quotation that already has quotation marks and a citation | Leave it. The match is expected. |
| Common wording, a technical term, a title or a reference-list entry | Leave it. Many texts share this wording and it does not need fixing. |
Two mistakes are common at this step:
- Swapping a few words to make the highlight go away. The sentence still follows the source, and the idea still needs a citation. Rewrite it properly instead. See how to paraphrase without plagiarizing.
- Deleting the sentence but keeping the idea. If the point came from a source, the source still needs to be named.
If you need to build a reference, our citation generator can help. For the habits that prevent these matches in the first place, see how to avoid plagiarism.
Manual checks that need no tool
You can check parts of a paper by hand. These checks are slower than a tool and only cover what you think to look for, but they catch things a tool does not.
Search an exact phrase in quotation marks
Pick a distinctive phrase from a sentence you are unsure about and search for it inside quotation marks. Google’s help page on refining searches says that to search for an exact match of a word or phrase, you enter it inside quotes. If the phrase comes back in a source you read, you know where the wording came from.
Keep the phrase short and unusual. A whole paragraph rarely returns anything, and a common phrase returns too much.
Compare your draft with your notes and sources
Open your notes next to the draft. Look for sentences that moved from a source into your notes and then into the paper without quotation marks. This is how a lot of accidental plagiarism happens.
Check that every citation has a reference
- Every in-text citation should have an entry in the reference list.
- Every entry in the reference list should be cited somewhere in the text.
- Every quotation should have quotation marks and a citation.
- Every figure, statistic and specific claim from a source should name that source.
How to read the percentage
There is no universal safe number. The percentage is the share of your text that matches other sources, and it counts cited quotations the same way as copied sentences.
- A higher number can be fine. A paper that quotes and cites many sources will have matches.
- A low number is not a guarantee. One copied paragraph in a long paper is a small share of the text and still a real problem.
- Numbers differ between tools. Each checker searches different sources, so the same paper gets different scores.
If your school or publisher gives a guideline, follow it. Otherwise, judge the paper by its matches. Our guide on how to interpret a plagiarism report goes through this in detail.
Checking in Google Docs and in the browser
You do not have to copy your text into another tab to check it.
- In Google Docs. The Plagiarism Checker Plus Google Docs add-on checks a document for plagiarism, AI writing and grammar inside Google Docs.
- In the browser. The Chrome extension adds a Check button to web text boxes with 50 or more words, and it can check text you highlight on any page.
- On the website. The plagiarism checker links every matching source next to your text. The first check is free up to 1,000 words without an account, a check needs at least 30 words, and a free account includes 3,000 words a month.
Your text is never used to train AI.
What a plagiarism checker cannot find
A checker finds matching words. Anything that does not show up as matching words is outside what it can see.
- Ideas without matching words. If you took an argument or a structure from a source and wrote it entirely in your own words, there may be no match. It still needs a citation.
- Translated text. A passage translated from another language does not share words with its source.
- Sources it has not indexed. A printed book, a paper behind a login or a classmate’s unpublished essay may not be among the sources a checker searches.
- AI-written text. Text from an AI tool is usually new wording, so it often matches nothing. That is a different check. The AI detector gives each sentence a likelihood of being AI-written plus an overall score, and that score is a probability, not proof. Both checks can run in one report.
So a clean report does not prove a paper is free of plagiarism. You know what you read and what you used. The standard is whether you credited it, not whether a tool noticed.
Checking someone else’s work
The steps are the same when you check a paper you did not write, but your position is different. You cannot know where a sentence came from, so a match is a question to ask, not an answer.
- Teachers and instructors: see how to detect plagiarism in student essays for the signs worth a closer look and a fair process. The plagiarism checker for teachers page covers the tool.
- Editors and co-authors: read each match with the writer where you can. They can usually tell you at once whether it is a quotation, a source they forgot to cite, or shared wording.