Compare 8 plagiarism checkers honestly.

Because it's not, for every use case. If your university already has a 5-year Turnitin contract and 4,000 instructors trained on it, switching to Noplag would create more friction than the auditability benefit warrants. If you need to submit to Nature next month and they run iThenticate at submission, your iThenticate check happens regardless of what we ran first. Pretending otherwise would make these comparisons unreadable — and you'd notice immediately. Picking the wrong tool for your use case is the expensive mistake; balanced comparisons are cheaper than the wrong purchase.

Quarterly review (next: Q3 2026). Within-quarter revisions when a competitor ships a material change — Turnitin's October 2024 AI-detector pause at Yale + Hopkins + Northwestern triggered a same-week update to the AI-detection row. The methodology section of each comparison page tracks the revision history; the master table footer shows the last-updated quarter. Send corrections to compare@noplag.com — we publish them with a revision timestamp.

No. Vendor pre-publication review would compromise the comparison's independence — the competitor would request changes favoring their product, and the negotiation would shape the content rather than the evidence shaping it. We do publish corrections after the fact when a competitor (or any reader) points out a factual error, and the revision history is available on request.

When a vendor makes a marketing claim that independent evaluations have disputed — e.g. Originality.AI's 99% AI-detection accuracy claim, which independent tests have not reproduced — we report the claim but flag it [DISPUTED] with a citation to the dispute. Allows readers to see both the vendor's claim and the counter-evidence. Used sparingly; only for empirical claims with credible counter-evidence, not for marketing flourishes.

Because users searching “plagiarism checker” frequently land on GPTZero pages by mistake — the products are routinely conflated in marketing copy and reviews. Including GPTZero in the comparison map and explaining what it actually does (AI detection only, no plagiarism source-matching) saves the reader from making that mistake. Same reason we include Grammarly: it's a writing assistant with a plagiarism feature, not a plagiarism checker, and users confuse the two.

Eight products covers the search-volume majority — Turnitin (49% market share institutional), iThenticate (academic publishing standard), Copyleaks + Grammarly + Originality.AI + Quetext (consumer + SMB tiers), GPTZero (AI-only specialist). Tools with <1% search-volume share (PlagScan, Plagium, DupliChecker, etc.) aren't yet covered; we expand when reader requests + search-volume data justify it. Request additions at compare@noplag.com.

Public-facing pricing pages, scraped quarterly. Where pricing is “contact for quote” (Turnitin institutional, iThenticate volume tiers), we cite published deal-size ranges from analyst reports (Gartner, Forrester EdTech market summaries) + community discussions (Reddit r/highered, Educause member forums). Enterprise quotes vary by FTE + region; we publish the typical ranges, not specific quotes.

Three angles: vendor-published accuracy claims (taken at face value but flagged), independent academic evaluations (Liang et al. Stanford 2023 on ESL bias, Hans et al. 2024 on Binoculars methodology), and our own controlled tests on shared corpora (NeurIPS 2023 + 2024 detection challenges, the HumanEval-AI benchmark). Per-comparison page, we report all three and explicitly note when they disagree — typically vendor claims are 5–15% higher than independent evaluations.

Bold = product leads or ties on that row's dimension. The pricing-model row is intentionally bold-free because no single product leads on price across all use cases — flat-rate wins for high-volume users (Noplag, Grammarly), per-document credits win for institutional ad-hoc use (iThenticate), per-FTE wins for predictable annual budgets (Turnitin). “Best price” is meaningless without a usage profile.

Yes — we publish under CC BY 4.0 specifically for procurement reuse. Reference the page slug + publication quarter. We also offer a downloadable PDF version per page at /compare/exports for institutions whose procurement workflows prefer attached documents over linked URLs. Request the PDF at compare@noplag.com if you don't see your competitor of interest in the export library.