Technical SEO

Free Doctype Checker

Use our free doctype checker to check that your page declares a modern HTML doctype. Enter any web address below and get your result in seconds, with plain-English fixes.

Free. You see the verdict at once; add your name and email to read the full result. We only read what is public on the page.

What this doctype checker checks

Reads the very start of the page for its <!DOCTYPE> declaration and tells you whether it is the modern HTML5 one.

The doctype checker reads the very first tokens of the page and matches them against the HTML5 declaration, <!DOCTYPE html>, and the older HTML 4 and XHTML forms. It also notes when anything precedes the declaration, which can throw browsers into quirks mode.

Why use a doctype checker

Without a doctype, browsers fall back to "quirks mode" and can lay the page out differently from what you designed.

Developers maintaining legacy templates, owners whose layout looks different in different browsers, and agencies checking a migrated site. Use the doctype checker when a design behaves oddly for no clear reason.

How to use the doctype checker

  1. Paste the full address of the page you want to test into the box at the top of this page. Use the exact page you care about, such as your home page or a service page, because each page can give a different doctype checker result.
  2. Press the button and wait a few seconds. The tool fetches the page the way a visitor and a search engine would, then runs its checks. Nothing is installed, and you only need to enter your name and email to read the full result.
  3. Read the verdict and the plain-English notes, make the changes listed under the fixes, then run the test again to confirm the problem is gone. Keep a note of the date and the result so you can show progress.

How to read your doctype checker results

  • Pass means the modern HTML5 doctype is the first thing in the file.
  • Warning means an older doctype that still works but is outdated.
  • Fail means no doctype, so browsers render in quirks mode.

How to fix problems the doctype checker finds

  • Put <!DOCTYPE html> as the first line of every page.
  • Remove old XHTML or HTML 4 declarations.

Common mistakes

  • Letting a comment or stray whitespace sit above the doctype in old IE-era templates.
  • Copying an XHTML doctype into an HTML5 page.
  • Removing the declaration when minifying templates.

Want everything fixed in one go? Our free website grader checks 40+ things at once, and you can ask for a free quote if you would rather have a person do it.

Doctype checker for Cayman Islands websites

Many Cayman sites were built a decade ago and patched since. If a layout breaks on one visitor's phone or a hotel business centre PC, quirks mode is a common cause. A quick doctype checker run can save hours of debugging and a lost booking.

Ranking in the Cayman Islands is a local contest: Google treats a .ky domain as aimed at the territory, and it rewards pages that name the places people search for, such as George Town, Grand Cayman, West Bay and Seven Mile Beach. After you act on your doctype checker result, work through our SEO guides for Cayman businesses, read how the WebGuru features fit together, or see the pricing for the full report.

Cayman Islands local SEO checklist

  • Name the place in your headings and first paragraph: George Town, Grand Cayman, West Bay, Cayman Brac or Little Cayman, whichever you serve.
  • Keep your business name, address and phone number identical on your website, Google Business Profile, Facebook page and local directories.
  • Use a .ky domain where you can. Google treats country-code domains as a signal that your audience is in that country.
  • Add a Google Business Profile, ask happy customers for reviews and answer every review.
  • Write for local questions, such as hurricane preparation, work permits or ferry times, in the words your customers would use.

Further reading

Frequently asked questions

What is the correct doctype today?

<!DOCTYPE html>, the HTML5 doctype.

Does the doctype affect SEO?

Not directly, but rendering problems it prevents can hurt usability.

What is quirks mode?

A compatibility mode where browsers imitate old, inconsistent behaviour. A correct doctype switches on standards mode.

Which doctype should I use?

<!DOCTYPE html>. It is short, case-insensitive and works in every modern browser.

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