For most businesses, more than half of website traffic now arrives on a phone, yet a striking number of sites are still designed and reviewed primarily on a desktop monitor. The gap between how a site is built and how it's actually used is where most mobile conversion problems live, and they're rarely dramatic. They're small frictions that compound, invisible individually and expensive in aggregate.
Touch targets that are technically clickable but practically frustrating
A button that's easy to click with a precise mouse cursor can be genuinely difficult to tap accurately with a thumb, especially on smaller phones or for users with larger hands. The common guidance is a minimum touch target of around 44 by 44 pixels, but the more useful test is simpler: try completing your own site's main conversion action, one-handed, on an actual phone, without zooming in first.
Forms that were clearly designed for a mouse and keyboard
Dropdown menus that are painful to scroll through on a touchscreen. Date pickers that don't trigger the phone's native date interface. Input fields that don't specify the correct keyboard type, so a phone number field pulls up a full alphabetic keyboard instead of a numeric one. Each of these adds a few seconds of friction, and on a form with several fields, those seconds add up to a meaningfully higher chance of someone abandoning before submitting.
Pop-ups and overlays that are nearly impossible to close on a small screen
A close button rendered at eight pixels in the corner of a modal is a minor annoyance on desktop and a genuine obstacle on mobile, where imprecise tapping and a much smaller viewport make it easy to miss entirely, or worse, tap through to something else by accident. This is one of the more common patterns flagged in usability research on mobile experience, and it's one of the easier fixes available: generous tap targets on every dismissible element, no exceptions. The same applies to cookie banners and app-install prompts, which are often the very first thing a mobile visitor has to fight with before seeing any actual content.
Content that assumes a wider screen than it gets
Tables, comparison charts and multi-column layouts often get built for desktop first and then just shrink for mobile, which leaves text unreadably small or forces awkward horizontal scrolling on the exact content a visitor came to actually read and compare. These sections usually need a genuinely different layout on mobile, stacked cards instead of a table, for instance, not a smaller version of the same one.
The fastest way to catch these before launch
Test the primary conversion path, the actual sequence a real visitor follows to enquire, book or buy, on a real phone before a project ships, not just a browser resized to look narrow. Resizing a desktop browser window doesn't replicate touch interaction, and it's touch interaction where most of these problems actually surface. It's a five-minute check that catches the majority of what a full audit would eventually flag anyway, and it's exactly the kind of test built into every web design project before anything goes live.
Why these issues survive a normal review process
Most design reviews happen in a meeting room, on a laptop, with someone presenting a polished mockup or a staging link opened in a desktop browser. Nobody is being negligent, it's simply the natural environment most review processes happen in. The fix isn't a longer checklist, it's making a real phone part of the review itself, not an afterthought done after the design is already considered finished and approved. Ten minutes with an actual device, before sign-off rather than after launch, tends to catch more real problems than another round of feedback on a desktop mockup.