What is an AI Checker? Find the best tools here (2025)

AI checkers have become super important around 2025. Teachers, businesses, students - everyone wants to be able to check if a text is actually written by a person or if it's just ChatGPT spinning something up.

Let me walk you through what these tools actually are, how they work, and which ones are worth trying.

So what exactly is an AI checker?

An AI checker (also known as an AI detector or ChatGPT checker) is a tool that analyzes text to determine if it’s written by a human or by AI - like ChatGPT, Claude, Gemini, or other language models.

Here’s how it works:

• You paste your text (or upload a document)

• The tool analyzes language patterns, structure, and probability

• You get a percentage result: "85% AI-generated" or "15% human"

• Some tools also highlight specific sentences likely written by AI

Example: If a student submits an essay, the teacher can use GPTZero or Turnitin to check if it’s written by ChatGPT or if the student actually did the work themselves.

How do AI detectors work technically?

Okay, so here it is – AI checkers use machine learning and look at multiple factors simultaneously:

1. Perplexity

• AI text: Low perplexity – the text is predictable and "safe"

• Human text: High perplexity – more variation and surprises

Example:

• AI writes: "Climate change is a global issue demanding immediate action."

• Humans write: "Climate crisis? Probably the most urgent issue we’ve ever faced, no exaggeration."

2. Burstiness

• AI text: Even and consistent – all sentences are similar

• Human text: Varied – short and long sentences mixed

Example:

• AI: "The company was founded in 2010. It has grown rapidly. It now has 500 employees."

• Humans: "The company started in 2010. Since then? Explosive growth! From three guys in a garage to 500 employees today."

3. Language Patterns

• AI often uses: Generic phrases, formal language, repetitions

• Humans use: Slang, personal expressions, dialects, typos

4. Structure and Semantics

• AI: Perfect grammar, logical flow but sometimes shallow

• Humans: Varied grammar, deeper insights, personal perspectives

Why are AI checkers needed?

For Teachers and Universities Students use ChatGPT for essays and exams – it's just a fact at this point. Studies show up to 30% of students may have used AI tools for schoolwork in 2024. Teachers need tools like GPTZero and Turnitin to verify student work.

For Content Creators and SEO AI-generated content can result in lower quality and worse Google ranking. Content creators use tools like Originality.ai to ensure human content. Google ranks based on quality, not whether it's AI – but low quality is penalized.

For Employers Job applicants use ChatGPT for applications. HR departments need to assess authenticity.

For Journalism Fake information and AI-generated news spread. Editorial teams need to verify sources.

The 10 Best AI Detectors in 2025

1. GPTZero – Best for Education

GPTZero was founded by Edward Tian (Princeton student) in January 2023 and has become the most used AI detector in schools. Over 10 million users globally.

Why it’s good:

• 99.3% accuracy according to their own tests

• 0.24% false positive rate – extremely few incorrect markings

• Color-coded highlights showing exactly which sentences are AI

• Chrome Extension for Google Docs

• Integrations with Canvas, Google Classroom

Features:

• AI detection for documents up to 250,000 words

• Detects GPT-4, GPT-5, Claude, Gemini, DeepSeek

• Writing patterns analysis

• Batch processing for teachers

Prices:

• Free: 10,000 words/month

• Essential: $15/month – 150,000 words/month

• Professional: $35/month – 300,000 words/month + API

• Premium: $90/month – 1 million words/month

Best for: Teachers, students, educational institutions

Limitations: May have lower accuracy on technical texts and very short texts (under 300 words).

2. Originality.ai – Best for Content Marketing

Industry leader for content creators and SEO specialists. Combines AI detection with plagiarism check.

Why it’s good:

• 85-97% accuracy depending on the dataset

• 100% accuracy on GPT-4 content according to several independent studies

• Combines AI detection + plagiarism check in the same scan

• Team workflows and API

• Readability scores and SEO analysis

Features:

• Multiple detection modes: Standard 2.0, Turbo 3.0, Multi-Language

• Content score for Google ranking potential

• Team management (up to 5 users)

• Site-wide scanning via URL

Prices:

• Pay-as-you-go: $30 per 300,000 words (about 10 cents per scan)

• Subscription: $14.95/month (unlimited scans)

Best for: Bloggers, content writers, SEO agencies, publishers

Limitations: Not free, may miss paraphrased AI text.

3. Copyleaks – Best for Enterprises

Enterprise solution focused on scalability and integrations. Used by large organizations and universities.

Why it’s good:

• 87.5% accuracy according to GPTZero benchmarking

• Enterprise focus with robust API

• Integrations: Canvas, Moodle, Microsoft Teams, Blackboard

• Supports 100+ languages

• Combines AI detection + plagiarism + paraphrase detection

Features:

• Multi-layered detection

• Custom compliance workflows

• Batch processing for large volumes

• Developer-friendly with SDKs

Prices:

• AI Content Detector: $7.99/month (1,200 credits)

• Plagiarism Detector: $8.99/month (1,200 credits)

• Combined: $13.99/month (1,200 credits)

• Enterprise: Custom pricing

1 credit = 250 words

Best for: Large companies, universities, enterprise customers

Limitations: Higher false positive rate than GPTZero, expensive for small users.

4. Turnitin AI Detection – Best for Universities

The most established plagiarism checker globally with integrated AI detection. Used by 15,000+ institutions.

Why it’s good:

• Already installed in most universities

• Combines plagiarism + AI detection

• Institutional trust and acceptance

• Robust database

Features:

• Similarity reports with AI flagging

• Grade feedback integration

• LMS integration

• Minimum 300 words for AI detection

Prices:

• Institutional license (contact Turnitin)

• Not for individual users

Best for: Universities, colleges, high schools

Limitations: Requires institutional license, minimum 300 words.

5. Undetectable.ai – Best for Content Creators

Unique tool combining AI detection with "humanization" – can rewrite AI text to make it human-like.

Why it’s good:

• Combines detection + humanizer

• Tests against 8 major AI detectors simultaneously

• Nominated by Forbes as the best AI detector

• Multi-language support (50+ languages)

Features:

• One-click testing against all major detectors

• AI Humanizer to rewrite AI text

• Chrome Extension

• API access

Prices:

• Free: Limited detections

• Essential: $9.99/month – 10,000 words

• Pro: $14.99/month – 33,000 words

• Business: $209.99/month – 308,000 words

Best for: Content writers who want to use AI but need to pass detectors

Limitations: Ethical questions around the "humanization" function.

6. Smodin AI Detector – Best Free Option

Offers free AI detection with relatively high accuracy and supports 100+ languages.

Why it’s good:

• Completely free for basic scanning

• 95% confidence on AI content

• 99% accuracy on human content

• Supports 100+ languages

• No registration required

Features:

• Real-time AI detection

• Sentence-by-sentence breakdown (with account)

• Detects ChatGPT, GPT-4, Claude, Gemini, Llama

Prices:

• Free: Unlimited basic scans (1,000 characters per scan)

• Premium: $10/month

Best for: Students, hobbywriters, budget-conscious users

Limitations: Lower accuracy than premium tools, character limits on the free tier.

7. Isgen.ai – Best Multilingual

Focuses on multi-language AI detection with 96.4% accuracy.

Why it’s good:

• 96.4% accuracy

• Near-0% false positive rate

• Works in ALL languages

• Detailed sentence-level analysis

• Color-coded highlighting

Features:

• Detects GPT-4, Claude, Gemini, Copilot, LLaMA, Grok, Mistral

• Explains WHY text is marked as AI

• Works in any language

Prices:

• Free tier: Limited scans

• Paid tiers: Information missing (new tool)

Best for: International users, non-English content

Limitations: Relatively new tool, less known.

8. DupliChecker AI Detector – Simple and Fast

Popular SEO tool suite with AI detection.

Why it’s good:

• Completely free

• Fast and simple

• NLP-based analysis

• No registration

Prices: 100% free

Best for: Casual users, quick checks

Limitations: Unknown accuracy rate, basic functionality.

9. NeuralWriter AI Detector – Quick Check

Focuses on speed and simplicity.

Why it’s good:

• Free

• Up to 10,000 characters per scan

• Detects ChatGPT, GPT-4, Bard, Gemini, Llama, Mistral

Prices: Free

Best for: Quick checks, short-form content

Limitations: Less known, limited research on accuracy.

10. SmallSEOTools AI Detector – SEO Focused

Part of the SmallSEOTools suite, focused on content creators.

Why it’s good:

• Completely free

• Unlimited checks

• Multi-language

• No registration

Prices: 100% free

Best for: SEO content creators, bloggers

Limitations: Unknown accuracy, less robust.

Who uses AI checkers?

Teachers and Schools Check student essays and exams, ensure academic integrity, identify ChatGPT use.

Recommended tools: GPTZero, Turnitin, Copyleaks

Best practice: Use AI checker as a starting point for conversation, not final proof. Combine with plagiarism check.

Content Creators and Bloggers Verify that content is human for SEO, avoid Google penalties, ensure quality.

Recommended tools: Originality.ai, Undetectable.ai, SmallSEOTools

Best practice: Scan everything before publishing, use AI as a help not ghostwriter.

Companies and Recruitment Verify authenticity in job applications, check writing samples, ensure authentic communication.

Recommended tools: Copyleaks, Originality.ai, GPTZero

Best practice: Use as a screening tool, follow up with interviews.

Journalists and Media Verify source authenticity, detect fake news, ensure journalistic integrity.

Recommended tools: Copyleaks, Originality.ai, GPTZero

Best practice: Cross-reference with multiple detectors, manual source verification.

Students Verify their own work isn't flagged as AI, learn differences, improve writing skills.

Recommended tools: GPTZero (free), Smodin, Undetectable.ai

Best practice: Scan before submitting, use as a learning tool.

Limitations – nothing is perfect

1. None are 100% accurate All AI detectors make mistakes sometimes:

• GPTZero: 99.3% accuracy = 0.7% error

• Originality.ai: 85-97% accuracy = 3-15% error

• Copyleaks: 87.5% accuracy = 12.5% error

Human text can be flagged as AI (false positive) or AI text can pass (false negative).

Solution: Use multiple detectors + human judgment.

2. AI evolves quickly When new AI models are released detectors need retraining. GPT-4 was released in March 2023 and many detectors initially missed it.

Solution: Choose tools that are regularly updated.

3. Gray area: AI-assisted vs AI-generated What counts as AI use?

• 100% AI: ChatGPT wrote everything → Easy to detect

• AI-assisted: Human wrote, AI edited grammar → Harder

• AI brainstorming: AI gave ideas, human wrote → Almost impossible

• AI as research: AI summarized sources, human wrote → Legitimate use?

4. Short text is harder AI detectors need about 300 words for reliable results. A tweet (280 characters) is impossible to determine.

5. Technical text looks AI-like Scientific abstracts, legal documents, and business communications often look "AI-like" even when human-written. Higher false positive rate.

6. Multilingual challenges Most detectors are trained on English:

• English: 95-99% accuracy

• Swedish, German, French: 80-90%

• Smaller languages: 60-80%

Solution: Use Isgen.ai or Copyleaks for non-English text.

7. Paraphrasing and "humanization" Tools like QuillBot and Undetectable.ai can rewrite AI text to avoid detection. It becomes an arms race between detectors and humanizers.

Frequently Asked Questions

Can AI detectors be 100% accurate? No. None are 100% accurate. Even the best have a 1-5% error margin. Use multiple detectors and combine with human judgment.

Can ChatGPT evade AI detectors? Partially. There are methods: paraphrasing tools, manual editing, mixing human + AI text. But good detectors can often find even paraphrased AI text.

Are AI detectors legal? Yes. But consider privacy concerns and GDPR – some tools store data.

What is the difference between AI detection and plagiarism check?

• AI detection: Checks if text is written by AI

• Plagiarism check: Checks if text is copied from other sources

Many tools combine both.

Can I trust free AI detectors? With caution. Free tools are OK for casual checks but have lower accuracy. For important cases, invest in GPTZero or Originality.ai.

Does Google penalize AI-generated content? Not directly. Google ranks quality, not how content is created. But AI spam and low-quality content are penalized.

Best practice: Use AI as a helper, add personal expertise, scan with Originality.ai.

How do I avoid my human text being flagged as AI? Tips:

• Vary sentence length – mix short and long

• Use personal expressions and anecdotes

• Include imperfections (fragments, ellipses)

• Use variety in word choice

• Add personal expertise

Which AI detector should I choose? Depending on use case:

• Teachers: GPTZero

• Content creators: Originality.ai

• Companies: Copyleaks

• Students: GPTZero Free / Smodin

• Budget: Smodin / SmallSEOTools

• Multilingual: Isgen.ai / Copyleaks

Summary

Top 3 in general:

1. GPTZero – Highest accuracy, best for education

2. Originality.ai – Best for content marketing

3. Copyleaks – Best for enterprise

Best practices:

• Use multiple tools for safer results

• Combine with human judgment

• Regularly update

• Read privacy policies

• Be transparent about AI usage

• Focus on quality, not just "passing the detector"

The future:

• Watermarking from AI tools

• Blockchain-based tracking

• Built-in detectors in Google Docs, Word

• EU AI Act and new laws

Find more AI tools at Aival.se

On Aival.se you'll find Sweden's largest collection of AI tools – 300+ reviewed tools for all uses. Everything from AI checkers to content creation tools, SEO tools and much more.

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Written by: aival.se