Every responsive page needs <meta name="viewport" content="width=device-width, initial-scale=1"> in its <head>. Without it, mobile browsers lay the page out in a virtual viewport, typically 980px wide, and shrink it to fit: media queries see 980px and text is tiny. width=device-width sets the layout viewport to the screen width in CSS pixels; initial-scale=1 starts at 100% zoom. Never add user-scalable=no or maximum-scale=1, which block the pinch zoom low-vision readers need (WCAG 1.4.4). viewport-fit=cover extends the page under a notch; then pad content with env(safe-area-inset-left) and its siblings. Head lists the other keys.