The short answer
Scribbr has a free AI Detector and a paid plagiarism report. You pay per document, from $19.95. If you check often, a monthly plan may cost less. If you check once, a single price may suit you. Five other tools below charge in other ways.
Who wrote this, and how. This page is published by Plagiarism Checker Plus. We make one of the tools on it. Ours is listed first, and the others are alphabetical. It is not a ranking. Facts about other tools come only from each maker’s own website, and the sources below show the day each was read. We did not run accuracy tests, so this page does not say which tool is more accurate.
What Scribbr offers
- AI Detector. Free, unlimited checks of up to 1,200 words each, no sign-up. Its page describes paragraph-level feedback.
- Plagiarism checker. $19.95 up to 7,499 words, $29.95 for 7,500 to 49,999 words, $39.95 for 50,000 words or more. Paid per check.
- Audience. Students and academics. Its page says it is not for copywriters, SEO or business owners.
Scribbr’s page also says universities may check work against private student paper databases it cannot access. See Turnitin alternatives.
Comparison table
Each cell is a fact from the maker’s own site. Prices are listed US dollar prices. Prices and limits change, so read the maker’s page on the day you buy.
| Tool | Free allowance | Paid price | Plagiarism check | AI detection |
|---|---|---|---|---|
| Plagiarism Checker Plus (ours) | First plagiarism check and first AI check free, up to 1,000 words each. A free account includes 3,000 words a month. | Student plan $4.99 a month, or $3.99 a month billed yearly. See pricing. | Yes. Every matching passage is linked to its source. | Yes. An overall score and a likelihood for every sentence. |
| Copyleaks | AI detector: up to 25,000 characters free. New users get free credits. The number is not stated. | Personal plan $16.99 a month, or $13.99 a month billed yearly at $167.88. | Yes. | Yes. Paid plans scan for AI and plagiarism in a single report. |
| GPTZero | 10,000 words a month and up to 10,000 characters a scan. Its plagiarism page says the free plan covers up to 10,000 words a month. Its support article lists Plagiarism Check under Premium. | The pricing page did not show readable prices for individual plans. | Yes. Its support article lists it from the Premium plan up. | Yes. Its home page describes color-coded highlights. |
| Grammarly | Free AI detector that shows a percentage. The limit is not stated. The plans page lists plagiarism detection in paid plans, not the Free plan. | Pro: $30 a month, $60 a quarter or $144 a year per member, from its help centre. Regional prices differ. | Yes, in a paid plan. It compares text with web pages and ProQuest’s academic databases. | Yes. The free tool gives a percentage. A paid AI Detector agent shows which parts may sound AI-generated. |
| Originality.ai | The pricing page describes the free plan two ways: 10,000 words (100 credits) once, and 60 credits a day for 3 scans a day. | Pro plan $14.95 a month, or $12.95 a month billed yearly at $155.40. | Yes. A scan for AI and plagiarism uses 2 credits per 100 words. | Yes. A scan uses 1 credit per 100 words. |
| QuillBot | AI Detector is free for all users. The plagiarism checker is not on the free plan. | Its help centre says the Premium price depends on your region. No price read. | Yes, with Premium. Up to 25,000 words a month. | Yes. |
How to choose
- Do you need plagiarism, AI, or both? They are different checks. Some tools charge for one and not the other.
- How long is your text? Compare it with the free limit. For one long paper, a per-document price may cost less than a subscription.
- Do you need sources linked? A percentage alone does not tell you what to fix.
- Do you want one number or sentence results? Sentence results give you more to look at. Treat any AI score as a likelihood, not as proof.
- What happens to your text? Read the privacy policy before you upload. We did not review other tools’ policies.
What we did not test
- Accuracy. We did not run the same text through each tool. We do not know which finds more or is right more often.
- What each free check really shows. We read the makers’ pages. We did not sign up and run a paper through each one.
- Pages we could not open on 1 November 2026. Copyleaks, QuillBot’s help centre and Scribbr did not open for our reader that day, so those facts are from 10 October 2026.
- Other tools. Leaving a tool out is not a judgement about it.
We also have an interest here: we would like you to try our tool. Its limits: it has no database of other students’ papers, it does not connect to a school system, and we publish no accuracy figure.
Sources
- Copyleaks (read 10 October 2026): pricing, plagiarism checker, AI detector.
- GPTZero (read 1 November 2026): home page, pricing, plagiarism checker, free and paid plans.
- Grammarly (read 1 November 2026): plagiarism checker, AI detector, plans, Pro price.
- Originality.ai (read 1 November 2026): pricing, plagiarism checker.
- QuillBot (read 10 October 2026): plagiarism checker plans, AI Detector, Premium price.
- Plagiarism Checker Plus: our own plagiarism checker, AI detector and pricing pages.