The html5 option was added in 2010 and marked as "not experimental" in 2011 but is not the default.

According to, current versions of all recent versions of all major browsers - even IE (9+) - support the HTML5 semantic elements (<section> etc.), except for <main> which IkiWiki doesn't use anyway. However, IE 8 is not a current version, but has ~ 4% market share and doesn't support <section> and friends; so there's still a compatibility concern there.

In particular, non-HTML5 mode uses <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" ""> which doesn't allow newer markup like the role attribute, so we can't close add aria landmarks to make ikiwiki websites more accessible while remaining XHTML 1.0 Strict. The recommended pseudo-doctype for HTML5, and for HTML with ARIA markup, is <!DOCTYPE html>.

(I do think we should continue to use <xml-compatible-tags /> and output well-formed XML so people who want to do XSLT tricks with IkiWiki's output can do so, though.)

In practice, real browsers have never actually implemented a strict XHTML mode: they've always parsed text/html as "tag soup", because they need a tag-soup parser anyway, and nobody wants to maintain two parsers.

Kai also wants a HTML5 doctype for more mobile friendly default themes.

Options include:

  • set html5 to 1 by default but retain the dual-mode templates, breaking IE 8 by default

  • remove the option and always behave as if it had been 1, simplifying the templates and breaking IE 8 unconditionally

  • either of the above and include html5shiv to de-break IE 8

  • change the doctype to <!DOCTYPE html> unconditionally, stop trying to limit ourselves to XHTML 1.0 Strict (use HTML5 features that degrade gracefully, like ARIA roles), but avoid using the new elements like <section> that require specific browser support unless html5 is set to 1. That would get rid of the backwards-compatibility concerns while keeping the ability to use post-2000 markup; we can use html5 to mean "be more enthusiastic about HTML5 features even if they might fail on older browsers".

Using the HTML5 doctype does mean we lose the ability to validate the output against a DTD (as wdg-html-validator does), but DTDs have very little to do with practical browser compatibility in any case.

Available in a git repository branch.
Branch: smcv/ready/html5
Author: Simon McVittie

At the moment my preferred option is the last, for which see my ready/html5 branch. I'll apply this at some point if there are no objections.


merged --smcv