Free GPT-4 Detector — Detect GPT-4, GPT-4 Turbo & GPT-4o
Detect text generated by GPT-4 and the GPT-4o series. 99.2% accuracy on unmodified output. No account required.
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How GPT-4 Text Is Detected#
GPT-4 and its descendants (GPT-4 Turbo, GPT-4o, GPT-4o-mini) produce the most stylistically polished and statistically predictable output of any current AI model. Low perplexity, uniform sentence structure, characteristic transition phrases (“Furthermore,” “In conclusion,” “It’s important to note”), and a measured, balanced register make GPT-4 text identifiable with very high accuracy.
Supported GPT-4 Variants#
- GPT-4 (base, March 2023 and later)
- GPT-4 Turbo (32K context variants)
- GPT-4o (omni-modal, mid-2024 onward)
- GPT-4o-mini (the engine that powers our own detector)
- GPT-4.1 and successors
GPT-4 vs GPT-3.5#
GPT-3.5 output is generally easier to detect than GPT-4 output because it has lower variance and more formulaic structure. GPT-4 produces more nuanced text with more varied sentence construction, but it still exhibits the multi-signal patterns our detector identifies. Detection accuracy stays high across both generations: ~99.5% on GPT-3.5 and ~99.2% on GPT-4.
Detecting GPT-4o Specifically#
GPT-4o (announced May 2024) produces text that is more conversational and slightly more bursty than earlier GPT-4 variants. Detection on GPT-4o requires updated signal calibrations, which our engine applies automatically.
Limitations#
Heavily edited or paraphrased GPT-4 text becomes harder to detect — the engine reflects this with lower confidence. Single-paragraph or very short GPT-4 output may not provide enough signal for reliable detection. See our methodology page for full details.