Search for "AI watermark detector" and you will find tools that promise three very different things. It helps to know which one you actually need before trusting a result.
Three different ideas hiding under one name
1. Invisible characters in text
Some generated text contains zero-width spaces, special non-breaking spaces, or control characters inserted between visible letters. These are real Unicode code points. A character scanner can find them, count them, and remove them. This is what this tool does.
2. Statistical watermarking
Methods like Google's SynthID Text change the probability of which token the model chooses next. No hidden character is inserted. Detection requires the same watermark key and configuration used during generation. A generic scanner cannot detect this.
3. Style-based AI detection
Some services try to guess whether a human or an AI wrote a paragraph based on writing style. These are heuristic estimates, not verifiable signals. They can be wrong and should not be treated as proof.
Why the name is confusing
Because "AI watermark" is used for all three, a tool that finds invisible characters can be mistaken for a tool that detects AI output. The honest thing is to separate them. This tool finds the first kind and tells you clearly when it cannot help with the others.
Bottom line: if you need to detect a specific vendor's statistical watermark, use that vendor's official detector or wait until they offer a public API. If you need to clean hidden characters from text, a character scanner is the right tool.