OmniDetect vs Grammarly: AI Detection & Plagiarism Comparison
One engine gives you a guess. Three engines give you certainty.
Try Free ScanTL;DR
OmniDetect Advantage
AI detection is a tiny add-on to a grammar tool — not their focus or expertise. No sentence-level breakdown, no consensus, no transparency into how scores are calculated.
Grammarly Strength
Grammarly is the world's most popular writing assistant with 30M+ daily users. AI detection is integrated into a tool many people already use.
The Verdict
Grammarly uses one detection model. OmniDetect runs GPTZero + Winston AI + ZeroGPT in a single scan and shows you when engines agree — and when they don't. That's the difference between a guess and a diagnosis.
Feature Comparison
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| Feature | OmniDetect | Grammarly |
|---|---|---|
| Detection | ||
| Detection Engines | 3 (GPTZero + Winston AI + ZeroGPT) | 1 (Grammarly proprietary) |
| Multi-Engine Consensus | ||
| Sentence-Level Highlighting | ||
| Analysis & Insights | ||
| AI Writing Coach (Advisor) | ||
| Edit & Rescan Loop | ||
| Score Delta Tracking | ||
| Verification Certificate | ||
| Shareable Verify Links | ||
| Privacy & Trust | ||
| No Text Storage (SHA-256 only) | ||
| Pricing & Plans | ||
| Free Tier | 3 scans/day | Basic grammar only (no AI detection) |
| Starting Price | $9.99 / 7 days | $12/month (Premium plan (includes all writing tools)) |
| Weekly Pass Option | ||
Independent Benchmark Data
Based on our 211-sample benchmark with real-world texts. Updated February 2026.
OmniDetect (3-Engine Consensus)
2.5%
FPR
96.1%
TPR
211 real-world samples · 3 independent engines · Updated Feb 2026
Grammarly does not publish independent accuracy benchmarks. OmniDetect provides transparent, verifiable accuracy data.
See full methodology and dataset details →Compare all AI detectors →
Why OmniDetect?
Three engines, one scan
GPTZero, Winston AI, and ZeroGPT run in parallel. When all three agree, you know the result is reliable. When they disagree, you know to investigate further.
Know WHY, not just WHAT
Our AI Advisor explains which sentences triggered detection and suggests specific rewrites. Not just a score — actionable guidance.
Pay for a week, not a month
Need it for finals week or a deadline? Our $9.99 7-Day Pass is the only weekly option in the market. No monthly commitment required.
Frequently Asked Questions
Does Grammarly detect AI content?
Yes, Grammarly has a basic AI detection feature in its Premium plan, but it uses a single proprietary model with no published accuracy data. It provides an overall AI score without sentence-level analysis. OmniDetect is purpose-built for AI detection, running 3 independent engines (GPTZero + Winston AI + ZeroGPT) with sentence-level highlighting and 96.1% verified true positive rate.
Is OmniDetect better than Grammarly for AI detection?
For AI content detection specifically, yes. Grammarly's AI detection is one feature among many in a grammar tool. OmniDetect is dedicated to AI detection with 3-engine consensus, sentence-level analysis, an AI Writing Coach, and independently benchmarked accuracy (2.5% FPR, 96.1% TPR). You can try OmniDetect free — no signup or subscription required.
Does OmniDetect check for plagiarism?
No — OmniDetect specializes exclusively in AI content detection. We believe focus beats feature bundling: our 3-engine consensus approach delivers higher AI detection accuracy than tools that spread resources across grammar, plagiarism, and AI detection. If you need plagiarism checking, use a dedicated plagiarism tool alongside OmniDetect for AI detection.
Can Grammarly detect ChatGPT writing?
Grammarly has a basic AI detection feature, but it uses a single unspecified model with no published detection rates for specific LLMs like ChatGPT, Claude, or Gemini. OmniDetect's 3-engine consensus achieves 96.1% true positive rate across all major LLMs, with sentence-level highlighting showing exactly which passages triggered detection.
Is Grammarly plagiarism checker the same as AI detection?
No — plagiarism detection and AI detection are fundamentally different. Plagiarism checkers compare text against existing sources to find copied content. AI detectors analyze writing patterns to determine if text was generated by an AI model. Grammarly offers both as separate features. OmniDetect focuses exclusively on AI detection with 3-engine consensus for maximum accuracy.
Is there a free alternative to Grammarly for AI detection?
OmniDetect offers free AI detection scans with no signup required — no need for Grammarly's $12/month Premium subscription. The free tier gives you real GPTZero-powered detection with sentence-level analysis. Upgrade for full 3-engine consensus reports starting at $9.99/week.