What to check
Does the widget resize properly on a small screen without covering the whole page or blocking the checkout button? Does the on-screen keyboard pushing up the viewport break the layout, hiding the send button or the most recent message? Test on an actual phone, not just a browser's device-simulation mode, which doesn't always replicate real mobile keyboard and viewport behavior accurately.
It's worth testing on more than one device if you can — an older Android phone and a recent iPhone can render the same widget noticeably differently, especially around keyboard behavior and safe-area insets near notches or home indicators.
Load speed matters more on mobile
Mobile connections are more variable than a home or office wifi connection — a widget that adds meaningful load time can hurt your site's overall performance and search ranking, since page speed is itself a ranking factor and mobile users are quicker to abandon a slow-loading page. Look for a lightweight script, not a heavy embedded iframe that pulls in its own large bundle of assets.
A well-built widget should load asynchronously, meaning it doesn't block the rest of your page from rendering while it loads — this is worth confirming directly, since a poorly implemented one can visibly delay your whole page.
Touch-friendly, not just responsive
Buttons and the send action need to be comfortably tappable with a thumb, not sized for a mouse cursor with pixel-precise clicking. This is easy to overlook if you only test on desktop during setup, where everything feels fine because a cursor is far more precise than a fingertip.
Small details matter here: adequate spacing between tappable elements, a large enough input field that doesn't require zooming to read what you've typed, and a send button that's easy to hit without also tapping something else by accident.
Why this is worth checking before, not after, launch
A broken mobile experience is invisible if you only ever test on your own laptop — you can go weeks without noticing, while a majority of your actual visitors quietly struggle with it. Spending five minutes on a real phone before considering setup complete catches this class of problem entirely, and it's five minutes well spent given how much of your traffic it likely affects.
