noplagApache 2.0
AN HONEST COMPARISON

Noplag vs Grammarly

These are not really the same kind of product. Grammarly is a writing assistant where plagiarism is one feature in the Premium bundle. Noplag is a dedicated plagiarism + AI-detection specialist. Most writers want both.

noplagOpen-source, since 2014OUR SIDE
GrammarlyWriting assistant, since 2009THE WRITING ASSISTANT
THE QUICK VERDICT

Choose Noplag if

  • You need a dedicated plagiarism + AI detector — not a writing assistant where plagiarism is one tab among ten
  • You need an API or self-host to embed plagiarism checks in your own product or pipeline
  • You want to see the matching algorithm — Apache 2.0 source on GitHub
  • You need citation-aware reports (quote / paraphrase / common knowledge / unattributed classification) — Grammarly returns a flat percentage
  • You need folder-level or library-wide duplicate scans — Grammarly is one-document-at-a-time
  • You need ESL-aware AI detection with documented methodology — not a single similarity percentage

Choose Grammarly if

  • Your primary need is writing assistance (grammar / tone / clarity) — plagiarism is a nice-to-have, not the headline
  • You want a browser extension that overlays suggestions while you write in your CMS, email, or docs
  • You're already paying $144/yr for Premium and the plagiarism feature is “included anyway”
  • You want GrammarlyGO generative-AI features alongside the plagiarism check
  • ProQuest dissertation database access matters for your discipline (Grammarly has it; Noplag uses open-access OpenAlex + CORE)
  • Your team needs unified writing-style governance — Grammarly Business is a real category leader; we don't compete there
FEATURE COMPARISON

The actual differences, line by line.

ACCESS & CONTRACTS
Individual access
NOPLAGYes · sign up in 30 seconds
GRAMMARLYYes · Free or Premium subscription
Pricing model
NOPLAGFlat-rate · $0 / $23 / $79 / Custom
GRAMMARLYWriting-assistant bundle · $12/mo annual or $30/mo monthly
Free tier (plagiarism)
NOPLAG2,500 words per check, forever
GRAMMARLYNone · plagiarism is Premium-only
Buy plagiarism without bundle
NOPLAGYes · $23/mo standalone
GRAMMARLYNo · bundled with Premium subscription
Procurement complexity
NOPLAGCredit card · self-serve · monthly
GRAMMARLYCredit card · self-serve · annual or monthly
DETECTION & ACCURACY
Auditable algorithm
NOPLAGApache 2.0 source on GitHub
GRAMMARLYClosed source · methodology not disclosed
Open-web pages indexed
NOPLAG150M+ · Google + Brave + Common Crawl
GRAMMARLY16B+ web pages (their crawl claim)
Scholarly database
NOPLAGOpenAlex + CORE + arXiv + PMC · 700M+ open-access
GRAMMARLYProQuest academic content (subscription)
Dissertation database
NOPLAGOpenAlex + CORE coverage
GRAMMARLYProQuest theses + dissertations (proprietary)
False-positive rate published
NOPLAGMeasured against PAN-PC-11 in CI
GRAMMARLYNot publicly disclosed (reviews note over-flagging)
AI-CONTENT DETECTION
AI detection available
NOPLAGComing soon · Premium tier · ESL-adjusted
GRAMMARLYYes · added 2023
AI detection method
NOPLAGBinoculars ensemble (Hans et al. 2024, open paper)
GRAMMARLYProprietary · methodology not disclosed
ESL-bias safeguard documented
NOPLAGYes · per-language eval + disclaimer
GRAMMARLYNot publicly addressed
Per-interval transparency
NOPLAGPer-sentence · interval-level drill-down
GRAMMARLYSingle similarity % · no per-interval breakdown
PRIVACY & DATA
Documents used to train models
NOPLAGNever · explicit policy
GRAMMARLYNot used for training (per Grammarly policy)
Right-to-erasure (GDPR)
NOPLAGOne-click in Settings
GRAMMARLYAccount-deletion flow
EU data residency
NOPLAGAvailable · Pro+
GRAMMARLYAvailable · Business+
Self-host / on-premise
NOPLAGYes · Apache 2.0 engine + Docker
GRAMMARLYNo · SaaS only
DEVELOPERS & INTEGRATIONS
Public REST API (plagiarism)
NOPLAGYes · OpenAPI 3.0 · $23/mo+
GRAMMARLYNo · plagiarism not exposed in Grammarly Business API
Webhooks
NOPLAGYes · Pro+
GRAMMARLYN/A · no plagiarism API
Browser-extension overlay
NOPLAGNo · standalone web app + REST API
GRAMMARLYYes · primary delivery channel
Multilingual coverage
NOPLAG5 languages at launch · per-language calibration
GRAMMARLYEnglish-primary · limited multilingual
PRICING REALITY

What plagiarism costs you in each tool.

Grammarly bundles plagiarism into Premium — you can't buy plagiarism standalone. Numbers below are direct from grammarly.com, May 2026.

noplagMOST FLEXIBLE
  • Free / self-host$0Apache 2.0 forever
  • Pro$23/moyearly · 500 pages/mo
  • Premium$79/moyearly · 5,000 pages/mo
  • EnterpriseCustomannual · unlimited pages
GrammarlyBUNDLE-ONLY
  • Free tierNo plaggrammar + spelling only
  • Premium (monthly)$30/mowriting + plagiarism bundle
  • Premium (annual)$12/mo$144 / year up-front
  • Business (per-seat)$15/seatannual · style governance
Grammarly pricing direct from grammarly.com/premium and grammarly.com/business, May 2026.
USING BOTH IS NORMAL

Grammarly + Noplag is the common stack. Each is the right tool for what it actually does.

If you write — keep Grammarly for the live grammar/tone/clarity coaching while you draft. Noplag is for the structured plagiarism + AI-detection pass before submission, where you need per-interval drill-down, citation classification, and an algorithm your IRB or editor can audit. We're not arguing for switching away from your writing assistant; we're arguing that the plagiarism feature inside it isn't enough when the stakes are higher than “my blog post.”

Read why use both
FREQUENTLY ASKED

Questions from writers comparing the two.

Are these really alternatives? Aren't they different products?
Mostly different products. Grammarly is a writing assistant — its core value is the live grammar/tone/clarity overlay in your browser while you draft. Plagiarism is bundled into Premium but isn't the headline feature. Noplag is a dedicated plagiarism + AI-detection product with citation classification, folder-level scans, API, and self-host. The honest answer for most writers: use both, for different parts of the workflow.
If I already pay for Grammarly Premium, why pay for Noplag?
If “plagiarism free” means “the percentage at the top of the Grammarly report” for your use case, you don't need us. Pay for Noplag when you need the things Premium doesn't have: citation-aware classification (quote vs paraphrase vs uncited), per-interval drill-down (not a single %), an API to integrate plagiarism into your editorial pipeline, folder-level dedupe across a content library, self-host for sensitive material, or AI detection with documented ESL safeguards.
Does Grammarly's 16B+ pages mean it catches more than Noplag?
Raw web-page count isn't the same as match quality. Grammarly indexes more pages but only does exact-and-near-exact match (their own reviews say they miss “patch writing” — synonym substitution). Noplag's cascade catches paraphrased matches that wouldn't surface in exact-match indexing. And on academic content, Noplag's OpenAlex + CORE + arXiv + PMC coverage is broader than Grammarly's ProQuest licensing for open-access work.
What about citation handling?
Grammarly's plagiarism check flags matches but doesn't classify them — a properly-cited quote and an unattributed paraphrase both show up as “matched.” Noplag classifies every interval as Direct quote (cited) / Paraphrase (cited or uncited) / Common knowledge / Bibliography / Original. The properly-cited intervals don't inflate your similarity score. This matters for academic writing where 30% “similarity” might be 90% legitimate citations.
How is Noplag's AI detection different from Grammarly's?
Grammarly added AI detection in 2023; methodology not disclosed. Noplag's AI detection is coming soon — it's on our roadmap, built on Binoculars (Hans et al. 2024, open paper) with per-language calibration and a documented ESL-bias adjustment that recalibrates the verdict for non-native English writers (Stanford 2023 paper measured 61.3% FPR on naive detectors). Both report a percentage; only Noplag will publish the why.
Can I self-host Noplag for confidential drafts?
Yes — Apache 2.0 engine, runs in Docker, no phone-home. Useful for unpublished manuscripts, sensitive corporate writing, or any draft that can't leave your network. Grammarly is SaaS-only — every keystroke goes to their servers (which is the price of the writing-assistant overlay).
Will Grammarly catch AI-generated text?
Their AI detector reports a percentage; that's about it. Limited methodology disclosure, no documented ESL safeguard. For most writers checking their own work, it's adequate. For institutional contexts where a student or employee might dispute the verdict, Noplag's coming-soon AI detection is designed around an auditable algorithm + ESL-adjusted scoring + per-sentence transparency — built to survive that conversation.

Keep Grammarly for the coaching. Use Noplag for the report.

Drop the draft you just finished in Grammarly into Noplag. Compare the plagiarism reports. Free up to 2,500 words, no signup. You'll see the gap in 60 seconds — and you'll decide whether the gap matters for your work.

Run a free checkRead why use both
Noplag vs Grammarly — an honest comparison