Best AI Detectors 2025: 7 Tools That Work

Written by
Ilias Ism

Reviewed by
Sophia Müller
Last updated: Jun 20, 2025
Everyone and their dog is pasting ChatGPT blurbs into essays. Teachers dread grading robots; bloggers fear Google penalties. You need a detector that says, "Yep, that paragraph's AI." Not a 2-page PDF of percentages.
Below are seven tools that actually caught my fake GPT-4 samples—ranked by how quickly they flagged the text, how clear the score felt, and how much they annoyed me with pop-ups.
Quick Take

- WriteHuman – Caught 8/10 GPT-4 snippets in under five seconds, dead-simple dashboard
- StealthGPT – Free checker nails obvious AI, speed king at <2 s per 300 words
- Winston AI – 99.98 % accuracy claim; love the teacher-style PDF reports.
- GPTZero – Keeps up with new OpenAI models per recent benchmark.
- BypassGPT – More a "humanizer," but its checker still spots sneaky phrasing.
- Undetectable.ai – Aggregates multiple detectors, decent if you dig meta-scores.
- StealthWriter – Dual humanizer/detector; flags lots of text but over-flags too.
(Want the longer SEO rant? Keep scrolling.)
1. WriteHuman – My Daily Driver
It just works. Paste text, get a blunt "Human / AI" bar. No login hoops.
4.9
Fast flagging and a one-click rewrite if you need to humanize.
Pros:
- ✅ 8/10 GPT-4 hits in tests
- ✅ Sub-5-second scans
- ✅ Clean, ad-free UI
Cons:
- ❌ Free tier caps at 1,000 words/day
- ❌ No batch upload yet
2. StealthGPT – Speed Demon (Free)
If you're broke or in a hurry, run your text here first. It's the quickest checker I touched and still nabbed 7/10 tricky snippets. Big green "likely AI" banner = nice.
4.8
The slick free checker that nails the basics.
Pros:
- ✅ Real-time scanning under 2 s
- ✅ Generous free tier
- ✅ Clear traffic-light score
Cons:
- ❌ Less reliable on >1 K words
- ❌ GPT-centric focus
3. Winston AI – Teacher Favorite
OCR uploads, PDF reports, and that bold 99.98 % accuracy pitch. In my test pack, Winston flagged 6.5/10 (rounded up for style points). Good pick if you grade essays all day.
4.3
Detailed reports & export-friendly PDFs for educators.
Pros:
- ✅ OCR for scanned docs
- ✅ PDF evidence reports
- ✅ Bulk upload
Cons:
- ❌ Slower (≈10 s/500 w)
- ❌ Premium plan needed for full export
4. GPTZero – Broad Coverage
GPTZero keeps pace with new LLM releases and stayed neck-and-neck with Winston in my tests. I still prefer its UI for quick vibes checks.
4.2
Covers GPT-3, GPT-4, Gemini, Claude—without drowning you in jargon.
Pros:
- ✅ Wide model support
- ✅ Handy highlight view
- ✅ Active dev updates
Cons:
- ❌ Free cap at 5K chars/day
- ❌ Occasional false positives on technical docs
5. BypassGPT – Edge-Case Specialist
Mostly marketed as a humanizer, but its checker caught 5/10 samples and gives a cool “risk slider.” Niche, yet handy for SEO pros playing cat-and-mouse.
3.9
For folks testing bypass tricks as much as detection.
Pros:
- ✅ Humanizer & checker combo
- ✅ CMS plugin options
- ✅ Risk-level slider
Cons:
- ❌ UI feels 2023
- ❌ Less accurate on long form
6. Undetectable.ai – Meta-Score View
Instead of one model, Undetectable pings multiple detectors and averages the risk. Great if you want a second opinion without 10 browser tabs.
3.6
One scan, multiple detector opinions.
Pros:
- ✅ Aggregates GPTZero, CopyLeaks, more
- ✅ API for batch jobs
- ✅ Decent humanizer
Cons:
- ❌ Mainly a bypass tool
- ❌ Free trial locked at 250 words
7. StealthWriter – Dual Tool, Mixed Bag
StealthWriter rewrites and detects, but its checker over-flagged my genuine blog paragraph. Use it when you mainly need the humanizer (it’s pretty good).
3.7
Solid humanizer with an okay detector baked in.
Pros:
- ✅ 10-level humanizer slider
- ✅ Built-in plagiarism scan
- ✅ Affordable starter plan
Cons:
- ❌ Over-flags legit text
- ❌ Slow on >1 K words
Pick One & Test It
Copy a chunk of your own ChatGPT text, run it through WriteHuman or StealthGPT, and watch the verdict. You’ll know in 30 seconds which detector fits your workflow.
Need more AI-marketing hacks? Check the deeper dive on /blog/seo-tools or explore the 30+ AI SEO statistics that reveal how AI is reshaping search. For slide geeks, check out our review of the /blog/best-ai-presentation-maker.
WRITTEN BY:

Ilias is a former CTO turned SEO strategist who specializes in building scalable content systems that rank, convert, and compound. He's founded multiple ventures including LinkDR (AI-powered backlinks), MagicSpace SEO (CRO-focused agency), AISEOTracker (SEO monitoring), and GenPPT (AI presentations).
He's led SEO and content projects for 50+ brands, producing growth systems that drive 300%+ organic traffic increases through systematic conversion psychology and technical optimization.
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