The five-minute manual check
- Text readable without zooming? Body text should be at least 16px on a phone.
- Can you tap everything? Buttons and links far enough apart that a thumb hits the right one.
- No sideways scrolling? Content that runs off the edge means a fixed-width element.
- Phone number tappable? It should start a call, not just sit there as text.
- Forms usable? Fields large enough, the right keyboard (numbers for phone), no captcha that fails on mobile.
- Pop-ups? Anything that covers the content on arrival and is hard to close is both annoying and penalized by Google.
- Speed on cellular data. Turn off Wi-Fi and reload. If it takes more than about three seconds to show the main content, see how fast a website should load.
The tools
- PageSpeed Insights (pagespeed.web.dev): paste the address, read the mobile tab. It shows real-user Core Web Vitals when enough visitors exist, plus a lab test with specific fixes.
- Chrome DevTools device mode: press F12 in Chrome, click the phone icon, pick a device. Good for checking every page quickly and for seeing what breaks at narrow widths.
- Google Search Console: the Core Web Vitals report groups your pages by whether real visitors on phones have a good experience.
- Lighthouse (built into Chrome DevTools): the same engine as PageSpeed Insights, with accessibility and SEO checks as well.
Google's old Mobile-Friendly Test tool was shut down on December 1, 2023, and the Search Console 'Mobile Usability' report went with it. Older articles still point to them.
What to do with the results
Most mobile problems come from a handful of causes: huge images, a theme or page builder that loads too much code, fonts that block rendering, and layouts designed only on a desktop. A developer can usually fix the first three without a redesign; the fourth is a design job. What responsive web design is explains what a properly built mobile site does.