Text watermark checker
Paste your text. See exactly which signals it carries, and where.
Your text
0 words3,000 words per free check
About this check
Invisible characters
Some tools mark text with characters that render as nothing: zero-width spaces, joiners, variation selectors, Unicode tag characters. They survive copy and paste, which is what makes them useful as markers — and what makes them findable. When we find them, the passage around each one is highlighted so you can see where they sit.
Vendor text watermarks
Google, OpenAI and Anthropic have each discussed watermarking generated text. None currently exposes a public interface for verifying one. Those checks therefore report 'Not verifiable' — the adapters are built and switch on the day an endpoint exists.
What a clean result means
It means these specific checks found nothing. It is not evidence that a person wrote the text, and it should never be used as such. Most AI-generated text carries no verifiable marker at all.