Text watermark checker
Invisible character detector and Unicode cleaner
An invisible character detector scans pasted text for supported Unicode code points that may not appear on screen. Watermark Tidy reports each type, count, and position before creating a cleaned copy from character types you explicitly select. The check is free, requires no account, and runs in your browser.
Open the private text checkerWhat the detector finds
The checker reads Unicode code points rather than guessing from how text looks. It reports exact matches and their positions so you can review them before removal.
| Category | Examples | Why it may be present |
|---|---|---|
| Zero-width characters | U+200B, U+2060 | Line breaking, copy residue, or hidden markers |
| Joiners and direction controls | U+200C, U+200D, bidi controls | Legitimate scripts, emoji, or text direction |
| Unicode tag characters | U+E0000–U+E007F | Machine-readable tags or intentional encoding |
| Variation selectors | U+FE00–U+FE0F | Emoji and standardized glyph variants |
| Unusual spaces | Non-breaking and thin spaces | Typography, formatting, or copied documents |
How to find and remove invisible characters
- Paste the text. The original remains in the input field and is not uploaded.
- Run the check. Review character names, Unicode code points, counts, and positions.
- Select supported matches. Nothing is selected by default; choose only character types you have reviewed.
- Create a cleaned copy. The tool changes only the selected supported matches and checks the copy again.
- Copy or download. Keep the original available until you confirm the cleaned text still reads correctly.
Hidden Unicode is not the same as a statistical AI watermark
A Unicode checker can prove that a particular code point is present. It cannot prove that ChatGPT, Claude, Gemini, or another model added it. Editors, websites, messaging apps, and document converters can insert the same characters.
Statistical systems such as SynthID-Text operate through patterns in token selection, not a fixed invisible character. Detecting those patterns requires the matching detector and is outside this tool. Removing Unicode characters alone does not remove or disprove a statistical watermark. The checker shows Claude's embedded watermark as “Not tested” until Anthropic publishes a compatible detector.
Read the guide to ChatGPT hidden characters and text watermarks.
Invisible character detector FAQ
What is an invisible character detector?
It scans text code point by code point and reports supported Unicode characters that may not render visibly. This tool shows their names, hexadecimal code points, counts, and positions.
Can hidden Unicode prove that text came from ChatGPT?
No. The same characters can come from formatting, editors, websites, languages, or manual input. A match cannot establish origin or authorship.
Will cleaning change visible text?
It can. Joiners, variation selectors, direction controls, and spaces may affect appearance or meaning. The tool keeps the original, shows findings first, and creates a separate cleaned copy.
Does it remove em dashes or rewrite wording?
No. Visible punctuation and wording are not hidden Unicode watermarks. The cleaner does not paraphrase, humanize, or rewrite text.
Is pasted text sent to a server?
No. The application disables form submission, browser spellcheck, storage, analytics, and application network connections. The scan runs locally.
Sources: Unicode Standard, Chapter 23 and Google DeepMind SynthID. Last reviewed August 12, 2026.