AI Detector is a web tool that judges whether a piece of pasted text was written by an AI. It combines three linguistic metrics — perplexity (how hard the next word is to predict), burstiness (variation in sentence length and complexity), and syntactic depth — and color-codes each sentence to show which parts look AI-generated. It covers more than ten models including GPT, Claude, Gemini, LLaMA, DeepSeek, and Mistral, and the official site claims 99.5% accuracy with a false-positive rate under 2%. No sign-up is required, and basic checks are unlimited. According to the site, it is used by more than 350,000 educators, students, writers, and businesses in total. The provider is Continuum LLC (United States).
Key Features
- Judgment based on three linguistic metrics: It combines perplexity, which measures how unpredictable each word is; burstiness, which looks at variation in sentence length and complexity; and syntactic analysis, which examines how deeply sentence structures nest. The premise is that human writing varies a lot, while AI writing tends to be average and too evenly polished
- Sentence-level scores with reasoning: Instead of returning a single overall number, it color-codes which sentences look AI-generated. That makes it easier to review only the suspicious parts rather than doubting the whole document, and it gives a starting point for revision or fact-checking
- Support for 10+ AI models: Output patterns from major generative models — the GPT family, the Claude family, Gemini, LLaMA, DeepSeek, and Mistral — are covered as detection targets
- Unlimited trials without registration: It works immediately without an email sign-up, and basic checks have no usage cap. Each submission accepts up to 5,000 words, and results come back within about ten seconds
- Batch processing and PDF reports on the paid plan: Batch processing of up to 100 files, PDF report export, saved check history, and a priority processing queue are included in the paid plan. Class management and per-student history features are also offered for educational settings
- Handling of submitted data: The official site states that input text is transmitted encrypted and is not stored permanently
Pricing
| Plan | Monthly price | What’s included |
|---|---|---|
| Free | $0 | No registration, unlimited basic checks, sentence-level scores, up to 5,000 words per submission |
| Premium | $19.99 | Unlimited checks plus 25+ detection methods, batch processing of up to 100 files, PDF report export, saved history, and a priority queue. Cancel anytime |
Pricing is current as of August 2026. Please check the official site for the latest details.
Pros & Cons
✅ Pros
- No registration or installation — open the URL, paste, and get a result. The barrier to entry is close to zero
- Because results are shown per sentence, you can work at the granularity of “only this paragraph looks suspicious,” which gives you something concrete to revise
- The metrics behind the judgment (perplexity, burstiness, syntactic depth) are published, so it feels less like a black box than many alternatives
- Even the free tier has no usage cap, so routine self-checks can often be handled without paying
- The paid tier is a single $19.99/month plan, which makes budgeting easier than credit-based pricing
⚠️ Cons
- The 99.5% accuracy figure and the sub-2% false-positive rate are self-reported by the official site; no independent third-party verification is available
- As with AI detectors in general, English written by non-native speakers and highly formulaic writing tend to be misjudged as AI-generated
- Results carry no legal or academic evidentiary weight. Using them alone to conclude that misconduct occurred is risky
- Each submission is limited to 5,000 words, so long papers and manuscripts must be split up
- Supported languages are not stated, so how well it performs on Japanese text cannot be judged from official information
- The operating company is not clearly identified on the site, which calls for caution when handling internal corporate documents
Comparison with Similar Services
| Item | AI Detector | GPTZero | Originality.ai | Copyleaks |
|---|---|---|---|---|
| Primary use | Quick checks for individuals and classrooms | AI detection for educational institutions | AI detection plus plagiarism checks for web content creators | Integrated checks for enterprises and institutions |
| Free tier | Unlimited (no registration) | A monthly free word allowance | Only a small credit grant at signup | Limited |
| Pricing model | Single monthly plan | Monthly subscription (multiple tiers) | Credit purchases plus monthly plans | Monthly subscription (multiple tiers) |
| Plagiarism check | No | Yes (depends on plan) | Yes | Yes |
| Sentence-level view | Yes | Yes | Yes | Yes |
| Intended scale | Individual to small team | Individual to institution | Individual to production team | Enterprise and institution |
Competitor pricing varies between vendor announcements and review articles, so always confirm the latest terms on each official site before deciding.
Who Is It For
- Students and writers who want to check whether their own text will trip an AI detector before submitting it
- Educators looking for a free, quick first-pass screening tool for assignments and reports
- Editors who want a rough sense of how much of an outsourced writer’s deliverable may be AI-generated
- People who prefer to cross-check with several detection tools rather than trusting a single result
- Anyone who simply wants to try out how AI detection works before paying for anything
Summary
AI Detector’s greatest strength is how easy it is to try: no registration, no usage cap. It publishes the basis for its judgments — perplexity, burstiness, and syntactic depth — and shows results per sentence, which gives you a concrete clue about what to revise.
At the same time, AI detection is inherently incapable of certainty. The stated accuracy is self-reported, and no independent verification has been published. In education and hiring in particular, treating a result as standalone proof of misconduct should be avoided. The realistic way to use it is as a guide for spotting passages worth a second look, combined with a final human judgment.