AI-generated content is everywhere now. Essays, reports, cover letters, product descriptions — you name it. And while using AI tools like ChatGPT isn’t a surprise anymore, figuring out whether a piece of text was written by a person or a machine is becoming a real challenge.
That’s exactly why AI detection tools are gaining so much attention. Whether you’re a teacher checking student papers, a recruiter reviewing job applications, or a content editor looking for originality — these tools promise to tell you when AI is involved.
There are a lot of options out there, but I wanted to know: which detector actually works best? So, I tested 5 of the most popular AI detection tools available in 2025:
- Smodin;
- ZeroGPT;
- QuillBot;
- GPTZero;
- Copyleaks.
One of the tools I was especially curious about was Smodin ai detector. It’s often mentioned for its simplicity and accuracy — so I really wanted to see how it compared to the rest.
In this article, I’ll break down exactly how I tested each tool, what worked, what didn’t, and which detector impressed me the most.
How I tested these tools
To keep things fair, I tested every AI detector in the same way. I used three types of text for each tool: one written entirely by a human, one fully generated by AI, and one hybrid — AI text edited and reworked by a human. Then I paid attention to what really matters when you’re checking content:
- How easy it is to use the tool;
- How fast it gives results;
- How clear and readable those results are;
- And most importantly — how accurate the detection feels.
Bonus points if the tool offered something extra — like highlighting AI-generated parts or breaking down the text in detail.
AI Detector Reviews: How Each Tool Performed
Each AI detector I tested had its own strengths and weaknesses. Some tools focused on speed, others on detail. Some felt very user-friendly, while others were more technical or limited in features. Here’s a breakdown of how each tool performed in my tests — what worked well, what didn’t, and what stood out along the way.
1. Smodin
Smodin offers a clean and user-friendly interface. You can paste text or upload files in .doc, .docx, .pdf, .xls, or .csv formats. The free plan allows 5 checks per week (up to 5,000 characters each). Paid plans start from $9/month (annual billing). It also supports over 100 languages.
One of the best features is how results are displayed. Smodin highlights AI-generated parts, shows the percentage of AI vs human content, and provides a confidence score — all in a clear and simple layout.
Test results:
- Human-only text: 100% human
- AI-only text: 98% AI-generated
- Hybrid text: 60% AI and 40% human, with accurate highlighting
Smodin handled all tests accurately, especially in detecting mixed content without over-flagging human edits.
2. ZeroGPT
ZeroGPT has a basic and not very intuitive interface. However, it offers a generous free limit — up to 15,000 characters per check. It supports all languages and allows file uploads. The tool highlights AI-generated parts and shows the percentage of AI vs human content. The main drawback is accuracy — it often overestimates human writing.
Test results:
- Human-only text: 96.3% human, flagged some natural sentences
- AI-only text: 59.1% human — missed many AI parts
- Hybrid text: 72.5% human — caught some AI sections, missed others
ZeroGPT is fine for quick free checks, especially for longer texts, but its detection accuracy is limited.
3. QuillBot
QuillBot is simple and easy to use. You can paste text or upload a file. It supports only 5 languages but is completely free with no character limits. The tool highlights suspected AI-generated sentences and marks confidence as high or low. It also breaks down text into:
- AI-generated
- AI-generated & AI-refined
- Human-written & AI-refined
- Human-written
Test results:
- Human-only text: 100% human
- AI-only text: 42% human, 58% AI — better than ZeroGPT but missed a lot
- Hybrid text: 100% human, didn’t catch AI-refined parts
QuillBot works well for fully human text but struggles with AI and hybrid content. A good free option for basic checks, but not for deeper analysis.
4. GPTZero
GPTZero has a clean but slightly overloaded interface. It’s packed with details, which isn’t ideal if you just want a quick AI vs human percentage. The free version lets you check up to 5,000 characters.
Without registration, you only see the overall result — AI, mixed, or human. To get full reports with highlighted sentences, you need to sign up. Registration gives 5 detailed reports for free. AI-generated sentences aren’t highlighted in the free version, which makes analysis less clear.
Test results:
- Human-only text: 100% human
- AI-only text: 42% human — missed a lot of AI content
- Hybrid text: 100% human — didn’t catch AI sections
GPTZero works well for human text but often fails with AI and hybrid content. Better for detailed reports than quick checks.
5. Copyleaks
Copyleaks has a simple and pleasant interface, easy to use even for quick checks.
The free version shows the percentage of AI content and highlights suspected AI sentences. For a detailed report, a paid plan is required — starting from $7.99/month (annual billing), with limited credits.
The tool supports many languages but offers only average accuracy.
Test results:
- Human-only text: 100% human
- AI-only text: 55.75% human — missed many AI parts
- Hybrid text: 85% human — detected some AI but missed a lot
Copyleaks is user-friendly and affordable but not the most accurate option for detecting AI content.
Final Thoughts: Which AI Detector Worked Best?
All five tools I tested have their strengths and weaknesses.
ZeroGPT and QuillBot are good for quick, free checks but often struggle with accuracy, especially on AI-only or mixed texts. GPTZero and Copyleaks offer more detailed analysis but require registration or payment for full reports.
Smodin stood out for its balance of accuracy, clear results, and user-friendly design. It handled all text types well, especially hybrid content, and made it easy to understand what was detected and why.
If you need an AI detector for occasional checks, any of these tools could work. But if accuracy and clarity matter most — Smodin showed the most reliable results in my tests.