Corrupt an HTML File Online
Corrupt an .html file online for free. Injects invalid byte sequences and breaks tag structure so the page renders as garbage or fails to load.
- No upload
- No size limit
- No sign-up
Corrupt your HTML file
Tuned for .html, .htm, .xhtml, and works with every other format too.
Why HTML files are hard to corrupt properly
HTML is the most forgiving format in common use. Browsers are built to render broken markup rather than reject it, so a file with mangled tags still displays something. Making an HTML file genuinely fail means attacking the encoding, not the markup.
What this tool destroys
- Character encoding. Invalid UTF-8 sequences are injected, so the browser's decoder produces replacement characters across the document.
- The doctype and head. The opening bytes containing the doctype and meta charset declaration are destroyed.
- Tag structure. Angle brackets and attribute quoting are broken up throughout the body.
- Inline scripts and styles. Embedded CSS and JavaScript are damaged along with the markup, so nothing recovers the layout.
What you will see afterwards
| Application | Behaviour |
|---|---|
| Chrome / Firefox / Safari | Renders a wall of mojibake and replacement characters instead of the page. |
| HTML validators | Report encoding errors and hundreds of structural failures. |
| Static site generators | Fail the build on the malformed source file. |
| Email clients | Render the HTML body as unreadable text. |
Common reasons people do this
- Testing that a CMS import path rejects malformed HTML.
- Verifying an HTML sanitiser or scraper does not crash on broken input.
- Demonstrating what encoding corruption looks like to a web class.
- Producing broken source files for a build-pipeline failure test.
How to corrupt a HTML file
- Drop your .html file onto the box above, or click to browse.
- Leave the level on Standard unless you want partial damage (Light) or need to defeat recovery software (Heavy).
- Press Corrupt file. Processing happens on your device, so it finishes almost immediately.
- Download the result. It keeps the original filename and byte length by default.
HTML FAQ
Why does the browser still show something?
Browsers never refuse HTML. They recover from anything. What you get instead is a page of replacement characters, which is what real encoding corruption produces.
Will it break the CSS and JavaScript too?
Any CSS or JavaScript inline in the file is damaged with it. Linked external files are separate and untouched.
Can I corrupt only part of a page?
Light level touches roughly 0.5% of the payload, which typically damages some sections while leaving others readable.
Does it work on XHTML?
Yes, and XHTML fails harder. It is parsed strictly, so a broken document is rejected outright rather than rendered.