# Legacy doctype. Expected “”.
> Canonical HTML version: https://rocketvalidator.com/html-validation/legacy-doctype-expected-doctype-html
> Attribution: Rocket Validator (https://rocketvalidator.com)
> License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/)
A legacy doctype triggers this warning because the document uses an older or non-standard `` declaration instead of the simple HTML5 doctype.
The HTML5 doctype is ``. It is case-insensitive, short, and tells the browser to render the page in standards mode. Older doctypes, such as those referencing XHTML 1.0 Transitional, HTML 4.01 Strict, or any DTD URL, are considered legacy. They still work in browsers, but the W3C validator flags them because the modern HTML standard requires only ``.
Common legacy doctypes that cause this warning include:
- ``
- ``
- ``
The fix is to replace the entire doctype line with ``. No DTD reference or public identifier is needed.
## HTML examples
### Before (legacy doctype)
```html
Example
Hello world
```
### After (HTML5 doctype)
```html
Example
Hello world
```