HTML Steganography Extractor
Find hidden messages in HTML files. Detects zero-width characters, comment encoding, whitespace patterns, and more. Auto-detect mode, CTF flag detection, AES decryption.
Drop HTML file or click to browse
.html, .htm, .svg, .xml — max 50 MB
How to Find a Hidden Message in an HTML File (5 steps)
- Upload a suspicious HTML file or paste the HTML source
- Click Auto-Detect — the tool tries all 6 extraction methods
- Review the results table — look for Plaintext or File output
- If encrypted, enter the password to decrypt
- Copy the extracted message or download the hidden file
HTML Steganography Methods — Detection Guide
| Method | CTF Frequency | Detection Risk | Capacity |
|---|---|---|---|
| Zero-Width Characters | Very High | Medium (hex view) | High |
| HTML Comments | High | Medium (view source) | Medium |
| Whitespace / Newline | Medium | Low | Medium |
| Attribute Order | Low | Very Low | Low |
| Case Variation | Low | Very Low | Low |
| Entity Substitution | Rare | Lowest | Low |
Frequently Asked Questions
How do I know if an HTML file has hidden data?
Upload or paste the HTML — the tool immediately shows a Zero-Width Character count and an Anomaly Score (0–100). A score above 40 indicates likely steganographic content.
What is a zero-width character?
Zero-width characters are Unicode code points (U+200B, U+200C, etc.) that are completely invisible in browsers, editors, and when copying text. They are the most common HTML steganography technique in CTF challenges.
The auto-detect returned noise — what does that mean?
The extracted bytes have high entropy but are not valid UTF-8 text or a known file format. This usually means the payload is AES-256 encrypted. Try entering a password.
Can I decode HTML files encoded by other tools?
This tool decodes HTML files encoded by the HTML Steganography Hider using any of the six supported methods. For files encoded by other tools, use Auto-Detect which tries all methods.
Is my HTML sent to a server for analysis?
Never. All extraction and analysis runs 100% in your browser. Your HTML source never leaves your device.
What is the Clean HTML Export feature?
It downloads a copy of the HTML with all zero-width characters, suspicious comment patterns, and encoding artifacts removed — useful for cleaning a page of hidden data.