Performance check
Doctype
Looks at the first thing in the HTML, after any comments.
- Category
- Performance
- Importance
- Low importance
- Check id
- doctype
How the result is decided
- Pass
<!DOCTYPE html>. - WarningAn older doctype, such as HTML 4 or XHTML.
- FailNo doctype, which puts browsers in quirks mode.
Why it matters
In quirks mode browsers imitate old rendering bugs, which can break layouts in ways that are hard to debug.
How to fix it
Make <!DOCTYPE html> the very first line of every page template.
After the fix, open the page’s report and choose Run again to confirm it passes.