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// Troubleshooting · Mobile

Why is your Shopify store not working on mobile?

By Published Updated 7 min read

Last updated 28 September 2026.

Because a phone is a different environment from your laptop: touch events instead of clicks, a viewport a third the width, widgets that exist only on mobile (sticky bars, drawers, swipe galleries), and iOS Safari's own rules for viewport height and fixed positioning. The four usual causes, ranked: click-only JavaScript handlers, an overlay whose close button lands off-screen, a broken mobile-only widget, and a Safari layout quirk hiding the buy button. Test on a real phone over mobile data — a resized desktop window shares the desktop's mouse events and JavaScript engine and misses exactly these.

// What a mobile-only failure costs you

Your share is in Shopify admin → Analytics → Sessions by device. Any currency — the maths is the same.
One broken mobile hour—average → peak-hour range
One broken mobile day—a silent weekend is two or three of these
Enter both numbers to see what a dead mobile add-to-cart costs while your desktop checks all pass.

method: monthly ÷ 730 hrs × mobile share = avg mobile hour · peak hour = 2–3× avg · day = monthly ÷ 30.42 × share — the same maths as our downtime cost calculator. Nothing is uploaded.

Every class of store breakage has a detection lag, and mobile's is the longest. Desktop bugs get caught fast because that's where merchants live. Mobile bugs are witnessed only by customers — who don't file bug reports, they just leave.

The store its owner checks is the desktop one; the store most customers use is the phone one — so the majority experience of a store is the one that gets tested least.

The Bilby scan screen mid-visit on the demo store
The scan screen mid-visit on our labelled demo store, Fernwick & Co.: a screenshot per step as it lands, then the seven things it checks read the recording. Run it on your store: free, about a minute, no signup, we never touch your store. Run the free scan →

The mobile-only failure classes, ranked

1. Touch-event JavaScript bugs

Buttons wired to mouse-specific events (or drag and hover interactions) that never fire on touch. Signature: tapping does nothing on the phone while clicking works on desktop. Often introduced by an app update or a theme customisation that tested fine — on desktop.

2. Viewport and overlay traps

The popup that's dismissible on a big screen can render its close control off-screen at phone width — a cookie bar, email popup or sale banner becomes a wall in front of the buy button. Test your own popups on a phone with the keyboard open; that's when the viewport is smallest.

3. Mobile-only app widgets

Sticky add-to-cart bars, mobile menus, swipe galleries and cart drawers exist only on mobile — so when they break, desktop testing literally cannot see it. A cart drawer that won't open is a checkout outage for every phone user.

4. iOS Safari quirks

Safari on iOS handles viewport height (the URL-bar collapse), fixed positioning and some input behaviours differently from Chrome. A layout perfect on Android can hide its checkout button behind Safari's toolbar. If you test on one phone only, make it an iPhone — and ideally test both.

The mobile test ritual

After every change, on a real phone, in a private tab, over mobile data — six taps, about two minutes:

  1. Homepage loads fast and nothing overlaps or covers content.
  2. Any popup or cookie bar can actually be dismissed with a thumb.
  3. Product page: the gallery swipes, the variant picker taps, the price is right.
  4. Add to cart responds to a tap and the item lands.
  5. The cart drawer or page opens and updates.
  6. Checkout reaches the payment step with the keyboard open.

A resized desktop browser window is not a mobile test — it shares the desktop's JavaScript engine and mouse events, missing exactly the touch-handler and Safari-specific failures that break real phones.

What a mobile-only failure costs

Put your monthly revenue and your mobile share into the calculator beside the answer. The maths is the honest kind: your average hour is monthly revenue divided by 730, the mobile slice of it is that times your share, and a broken peak hour costs two to three times the average because sales cluster in evenings and weekends. A dead mobile add-to-cart approaches full-outage cost while every desktop check you run passes.

The ritual only works if it happens. Mobile checks get skipped exactly when changes are most frequent — launch weeks, sale prep, theme updates. Bilby visits your store every night at a phone viewport as well as a desktop one, in a real browser, and flags anything a customer would hit, with the phone screenshot attached; run the free visit now. It's the safety net under the ritual, not a replacement for shipping carefully.

Frequently asked questions

Why does my store work on desktop but not on mobile?
Mobile is a different environment: touch events, a tiny viewport, mobile-only widgets, and iOS Safari's quirks. The frequent concrete causes are click-only JavaScript handlers, overlays with unreachable close controls, broken drawers or sticky bars, and Safari viewport issues.
How do I test properly on mobile?
Real phone, private tab, mobile data — visit the six-step ritual above by tapping. Test iPhone Safari and Android Chrome if possible; they fail differently. A resized desktop window is not a mobile test.
How much can a mobile-only bug cost?
Your mobile share of revenue, for every hour it runs. Enter your monthly revenue and the mobile share from Sessions by device into the calculator on this page; the method is printed under it.
Why do these bugs last so long?
The person most likely to check the store checks it on desktop, where everything works. Only the conversion graph — or an automated nightly visit at a phone viewport — tells on the mobile experience.

Keep reading: Add-to-cart not working? · The nightly store check · Images not loading? · Downtime cost calculator

// Related field notes

Keep reading

Breakage

7 Silent Shopify Problems That Kill Sales While You Sleep

Read the guide → Checkout

How Often Should You Test Your Shopify Checkout? (The Nightly Store Check)

Read the guide → Breakage

Shopify Images Not Loading? Every Cause, Fixed (2026)

Read the guide →

// The store most customers actually use

Is your store
okay on mobile?

Bilby visits your store at a phone viewport every night and reports anything broken — with the phone's screenshot. One free scan, no signup.

Scan my store free → How the Watch check works

Thin or missing product content is the other half of this problem, and it is the half search engines and AI assistants see. Navaal: AI SEO, AEO & GEO audits a Shopify catalogue for it free, and writes what is missing for review.