To check for plagiarism, paste or upload your text into a plagiarism checker, review every highlighted match against its source, and fix any passage that uses someone else's words or ideas without quotation marks or a citation. The similarity percentage is only a starting point. What matters is whether each match is properly attributed, which you can only judge by reading the report line by line.
What a plagiarism checker actually does
A plagiarism checker breaks your text into short sequences of words and compares them against a large collection of web pages, published articles and, for some tools, previously submitted papers. When a sequence in your document closely matches a sequence in that collection, it highlights the passage and links to the likely source.
A few consequences follow from how this works:
- Checkers find matching text, not stolen ideas. An idea taken without credit but written in new words may not be flagged at all.
- Results depend on what's in the database. Paywalled journals, print books and private documents may not be covered. Different tools can return different results for the same paper.
- Short common phrases ("on the other hand," "the results indicate that") match countless sources and are usually noise.
For a deeper look, see how plagiarism checkers work.
Step-by-step: checking your paper
Step 1: Finish your draft, including citations
Check a complete draft, with your quotation marks and in-text citations already in place. Checking a rough draft with missing citations produces a report full of matches you already knew about.
Step 2: Run the check
Paste your text or upload the file. If you're checking a long paper, make sure the whole document was processed, as some tools limit length per check. Keep a copy of the report.
Step 3: Look at the matches, not just the score
Open each highlighted passage and compare it with the linked source. Sort each match into one of four groups:
| Match type | What it looks like | What to do |
|---|---|---|
| Quoted and cited | In quotation marks, with a citation | Nothing; this is correct use |
| Cited but not quoted | Exact source wording, with a citation but no quotation marks | Add quotation marks, or rewrite as a genuine paraphrase |
| Not cited | Source wording or idea with no citation | Add a citation and either quote or paraphrase properly |
| Common phrase or reference entry | Short generic phrase, a title, or your reference list | Usually ignore |
The second group surprises many students. Copying exact words with a citation but without quotation marks is still a problem: it presents the source's phrasing as your own.
Step 4: Fix real problems
For each genuine issue:
- Exact wording you want to keep: add quotation marks and a page number.
- Wording you don't need to keep: close the source, rewrite the idea in your own sentence structure, then add a citation. Our guide on how to paraphrase shows the method.
- An idea or fact with no citation: add one, even if your wording is original.
- A passage you can't trace to a source in your notes: find where it came from before submitting. If you can't, cut it.
Step 5: Re-read, don't just re-run
After editing, re-read the revised passages for sense and flow. Running the check again can confirm the fixes, but don't treat a lower percentage as the goal. Rewriting sentences just to change words, without adding attribution, hides the problem without solving it.
Reading a similarity report: common situations
"My score is high, but it's all quotes." If the matches are quotations you've marked and cited, that's not plagiarism. You might still ask whether you're relying on quotes too heavily, since instructors usually want more of your own analysis.
"My reference list is flagged." Reference entries look the same in every paper that cites the same source. Many tools let you exclude the bibliography; if not, ignore those matches.
"It matched a source I've never seen." Common phrasing or standard technical wording can match unrelated documents. Check whether the matching phrase is generic. If it's a distinctive sentence you wrote yourself, you can usually ignore the match.
"It matched my own earlier paper." If you reused your own work, you may need permission and a citation to your earlier paper. See our guide to self-plagiarism.
"The score is low, so I'm fine." Not necessarily. A low score means few word-level matches were found. It doesn't confirm that every idea is cited, and it doesn't cover sources outside the tool's database.
Checking without a tool
Software helps, but a manual review catches things checkers miss. Before submitting, go through your draft with your notes beside you:
- For each paragraph, ask: where did this idea come from? If it came from a source, is that source cited?
- For each statistic, date or specific finding, is there a citation?
- Search your notes for any exact sentences you copied. Are they in quotation marks in the draft?
- Does every in-text citation have a matching reference entry, and vice versa?
This takes ten or fifteen minutes for a typical essay and catches the most common source of trouble: notes that lost their quotation marks.
Checking work you didn't write
Teachers, editors and managers check plagiarism too. A few points of fairness apply:
- A match is a reason to look closer, not a verdict. Read the context before drawing conclusions.
- Writers sometimes match a source because they share common phrasing or cite the same quotation correctly.
- Talk with the writer. Drafts, notes and version history usually explain unclear cases quickly.
Plagiarism checks vs. AI detection
These are separate questions. A plagiarism checker asks, "Does this text match existing text?" An AI detector asks, "Does this writing resemble machine-generated text?" Original AI-generated writing may match nothing in a plagiarism database, and human writing can be flagged by an AI detector. If your course has an AI policy, follow it directly rather than relying on either tool to tell you what's allowed.
Key takeaways
- Run the check on a finished draft with citations already in place.
- Judge each match by its attribution, not the overall percentage.
- Fix problems by quoting, paraphrasing properly and citing, never by disguising text.
- Pair the software check with a quick manual review against your notes.
For prevention habits that make the check mostly uneventful, read how to avoid plagiarism.