Since most search engines prioritize the mobile version of your site, confirming it's genuinely usable on a phone is a foundational, checkable task.
Test on an Actual Device, Not Just a Simulator
Real-device testing over a real mobile connection catches issues that a desktop-based simulator sometimes misses.
Check That Content Matches Between Mobile and Desktop
If your mobile version hides or shortens content shown on desktop, that content is effectively invisible to a mobile-first crawl.
Look for Tap Targets That Are Too Small or Too Close
Buttons and links that are hard to tap accurately on a touchscreen hurt both usability and search performance.
Next step: Use the SEO Audit to include a mobile-friendliness check as part of your broader technical review.