AI Content Detector
Commercial use OK
380+ models
No watermark
No sign-up needed
Model:
+ GPT-5, Claude, Gemini
Honest note on AI detectors:
AI detectors are not reliable. Academic research (Stanford HAI, Vanderbilt, University of Maryland) shows false-positive rates of 5–15% on genuine student writing and false-negative rates that climb above 30% on modern models (GPT-4+, Claude, Gemini). Our score reflects pattern-matching heuristics (perplexity, burstiness, AI-tell phrasing), not ground truth. Do not use this to accuse anyone of academic misconduct. Use it to audit your own drafts or as one signal among many.
Verdict
Pattern-match score, not ground truth.
100% human
100% AI
AI-tell signals detected
Per-sentence confidence
Advanced options
Result
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Detect AI-generated text for free. Check if content was written by AI.
How to Use AI Content Detector
1
Enter your input
Type text, upload a file, or describe what you want. No account needed.
2
Click generate
Our AI processes your request in seconds using the best open-source models.
3
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Download, copy, or share your result. Free for personal and commercial use.
Use this tool via API
Automate this tool from your own code. OpenAI-compatible REST endpoint, Bearer-token auth, no extra SDK required. Token costs match the web interface.
curl -X POST https://api.free.ai/v1/chat/ \
-H "Authorization: Bearer sk-free-..." \
-H "Content-Type: application/json" \
-d '{"model": "qwen7b", "messages": [{"role": "user", "content": "Summarize this: ..."}]}'Related Free AI Tools
AI Content Detector — FAQ
Free.ai AI Detector scans text for linguistic fingerprints of AI generation — low burstiness, parallel triads, empty transitions, AI-tell vocabulary like "leverage" / "utilize" / "in today's fast-paced world" — and returns a 0–100 probability score, per-sentence confidence, and a labeled list of signals (AI-indicating or human-indicating). Pick a text-type pill (general / academic / blog / email / creative / code comments) so the model applies the right baseline.
Not reliably accurate. Stanford HAI (2023), Vanderbilt (2023), and University of Maryland (2024) studies all show false-positive rates of 5–15% on human writing and false-negative rates above 30% on modern LLMs (GPT-4, Claude 3/4, Gemini). OpenAI shut down their own detector in 2023 citing "low rate of accuracy". Turnitin's own documentation warns their AI score should never be the sole basis for an academic-integrity decision. Our tool is no exception — it's a pattern-matching heuristic, not ground truth.
Three legitimate uses: (1) Audit your own drafts before publishing — if YOUR writing scores 85% AI, you probably leaned on ChatGPT and should rewrite. (2) One signal among several when evaluating submissions — not a verdict. (3) Research into writing-style drift. Illegitimate uses: accusing students, gating job applications, flagging emails as "suspected AI". Do not do any of these with ANY detector (paid or free) — the error rates are too high.
GPTZero is $10–24/mo. Originality.ai is $14.95/mo or $0.01/credit. Copyleaks is $10.99/mo. Turnitin bundles AI detection into the $3+/paper institutional plan. Winston AI is $18/mo. All of them publish confident accuracy claims (95%+, 99%+) that independent academic research contradicts. Free.ai is free and we're honest: no detector beats 85% accuracy on mixed human/AI text; most fail below 75% on modern LLM output. Use ours as one signal, never as the sole basis for a decision.
We target the common fingerprints of GPT-3.5, GPT-4, Claude 3/4, Gemini, Llama, and Mistral outputs. Models that explicitly produce varied voice (prompted with custom system prompts, creative temperature, or fine-tuned on human writing) score lower even when they ARE AI. Models humanized via any humanizer tool (including ours at /text/humanizer/) also score lower.
Under ~100 words there isn't enough variance to measure burstiness (the signal that distinguishes AI's uniformity from human's natural variation). A two-sentence email could be AI or a quick human reply — there's no way to tell. Paste at least 200–300 words for a signal worth reading.
Burstiness = the variance in sentence length and complexity across a passage. Humans write bursty prose: a 40-word compound sentence followed by a 6-word punch. AI defaults to even sentences, 18–25 words each, similar complexity. Low burstiness + even cadence is a strong AI signal. BUT: formal academic writing and legal prose are also low-burstiness, which is why context matters.
Best accuracy in English (most linguistic research is English). Decent results on Spanish, French, German, Portuguese, Italian. Chinese, Japanese, Arabic work but with higher error rates because AI-tell patterns translate imperfectly. For low-resource languages, results are essentially random.
This is the detector's most common failure mode. Stanford showed non-native English writers get flagged as AI 61% of the time because their prose is naturally low-burstiness. If you're being accused of AI use based on ANY detector, push back — the tools do not have the accuracy needed to support that claim. Screenshot this FAQ and the academic citations above. If you want to lower your score without changing meaning, /text/humanizer/ can help.
Text is sent to Free.ai's self-hosted GPUs, analyzed, and discarded. We do not train on user inputs. We log only timestamp + token cost for billing — never the source text. Generation history (signed-in users) stores a 200-char preview; you can delete it anytime from /account/?tab=history.
No — first analysis is free, no email, no credit card. Sign up for 10,000 free signup tokens + generation history, higher daily caps, and access across all 400+ Free.ai tools.
Yes. POST to /v1/chat/ with the detector system prompt and parse the JSON response in your client. If you're building a product that uses AI detection, READ THE ACADEMIC CAVEATS above — do not build features that make accusations based on detector output alone. Full snippets at /api/.
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