Doctype missing

Opportunity severity, in the Content tab

Why it matters

Without a doctype browsers use quirks mode, which causes rendering differences.

How to fix it

Add <!DOCTYPE html> as the first line.

How Crawlune finds it

Crawlune flags Doctype missing automatically on every crawl and lists the affected URLs under the Content tab, where you can filter, inspect each page and export the list to CSV. The free version crawls up to 550 URLs with every check enabled.