Check text for the hidden and unusual Unicode characters commonly left behind by AI writing tools — and clean them in one click.
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No character is proof of AI authorship.When researchers reported in April 2025 that OpenAI's o3 and o4-mini models were inserting narrow no-break spaces (U+202F) into their output, OpenAI stated the behavior was "a quirk of large-scale reinforcement learning" — not a deliberate watermark. The forensic consensus is that these characters are training artifacts absorbed from high-quality typographic and multilingual sources.
Em dashes and curly quotes deserve special caution: they are standard professional typography. Microsoft Word and Google Docs insert curly quotes automatically, and skilled human writers have used em dashes for centuries. Treat them as stylistic context, not evidence.
What this tool gives you is the raw facts — exactly which unusual characters are present, where, and how often — so you can judge for yourself. For the full hidden-character analysis, use the invisible character detector.