Check for Claude Watermark — Free Text Scanner
Paste any text below to scan for Claude's distributional watermark signature. Results appear in real time with confidence scoring.
How Watermark Detection Works
Our scanner uses a multi-layer analysis pipeline to determine whether a piece of text carries Claude's watermark signature. The detection process examines three distinct signal channels:
1. Token Distribution Analysis
The primary detection method examines the statistical distribution of tokens across the text. Claude's watermarking system partitions the token vocabulary using a cryptographic hash function, creating "green" and "red" groups. During generation, the model biases its outputs toward green tokens. Our scanner computes the ratio of green-to-red tokens and compares it against the expected baseline for natural text. A statistically significant excess of green tokens indicates the presence of a watermark.
2. Homoglyph Substitution Scan
Some watermarking techniques replace standard ASCII or Unicode characters with visually identical alternatives from different Unicode blocks. For example, a Latin "a" (U+0061) might be swapped with a Cyrillic "a" (U+0430). Our scanner checks every character in the input against a database of known homoglyph pairs and flags any substitutions that could serve as watermark signals.
3. Zero-Width Character Injection
A simpler but surprisingly common watermarking approach involves inserting invisible Unicode characters at specific positions within the text. Characters like U+200B (zero-width space), U+FEFF (byte order mark), and U+200D (zero-width joiner) are invisible to readers but can encode binary data when placed in specific patterns. Our scanner strips and reports any such characters found in the input.
Interpreting Your Results
The scanner reports results with a confidence percentage. Scores above 85% indicate a high likelihood that the text carries a Claude watermark. Scores between 60% and 85% suggest the text may be partially watermarked or lightly edited from a watermarked source. Scores below 60% generally indicate clean text, though very short passages may not contain enough tokens for reliable analysis.
For best results, paste at least 200 words of text. The statistical analysis becomes significantly more reliable with longer passages because the token distribution pattern is easier to distinguish from random variation in shorter texts.
What If a Watermark Is Detected?
If the scanner detects a watermark, you can use our removal tool to strip it automatically. The removal process applies targeted synonym substitution and token redistribution to neutralize the statistical signal while preserving the meaning and readability of your text. You can also process multiple texts at once using our batch tool.