Missing mobile viewport

On every live page we look for <meta name="viewport">. If it is missing, the finding is raised. No threshold, no heuristic.

It is the same signal as STR-06 in the core set, and a page without a viewport gets both findings. The difference is only in what each text says about it: STR-06 explains that the viewport has no effect on what a model reads off the page; SEO-11 talks about mobile search. The duplication is deliberate: the modules are independent and share no configuration.

What the check does not do: it does not judge the value (width=1200 passes like a correct width=device-width), it does not test how the page actually looks on a phone, and it does not report user-scalable=no, which is an accessibility defect. The finding is page-level; severity is warning.

For visibility in AI answers the effect is none at all, and that is mechanics, not caution: the viewport is an instruction for rendering in a browser. The text in the HTML is identical with it and without it, so anything reading delivered HTML (which, by measurement, is most AI crawlers) cannot tell the difference.

Nor is it a condition for being indexed. Google says so in its own documentation: having a mobile version is not required for content to appear in Search results, though it strongly recommends one.

What Google does say unambiguously, and what matters more to you: it indexes the mobile version. It crawls with the smartphone agent. And it adds a requirement that matters far more than this element: the mobile site must carry the same content as the desktop one. When there is less on mobile, the lesser content is what Google works with.

The practical conclusion: it is a one-line fix, so make it. But the value is with visitors: without a viewport their phone renders the page at desktop width and scales it down to illegibility.

This line belongs in the <head> of every page, and nothing more:

<meta name="viewport" content="width=device-width, initial-scale=1">

• user-scalable=no and maximum-scale=1 do not belong there: they forbid zooming, and for somebody who needs to see the page that is a serious barrier.
• Nor does a fixed width (width=1024): you would be telling the browser to pretend it is a tablet.

The element alone does not make a site responsive, though. Add it to a page whose layout assumes a fixed width and you get a page that overflows sideways, often worse than a scaled-down desktop view. After adding it, open the page on a phone and check three things: nothing overflows horizontally, text is readable without zooming, and links can be hit with a thumb.

Horizontal overflow you find that way is reported separately by DSG-01, and small touch targets by DSG-05, if you have the design module enabled.