Viewport meta tagWhat it checks and how to fix it

What it checks

Reads the viewport meta tag on the homepage. It passes when the tag sets both width= and initial-scale=, warns when one of them is missing, and fails when the tag is missing or empty.

Why it matters

Without a viewport tag, mobile browsers render the page as if on a 980px-wide desktop screen and shrink it to fit, so text is tiny and visitors have to zoom. Google's mobile-friendly assessment and Lighthouse both flag it. It is one line of HTML.

How to fix it

Add this to the <head> of every page:

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

Do not add maximum-scale=1 or user-scalable=no: blocking zoom is an accessibility failure (WCAG 1.4.4) and iOS ignores it anyway.

In Rails, put it in app/views/layouts/application.html.erb (new apps include it already).