Upsell pop-ups on mobile: what makes customers close them

September 18, 2026 · 2 min read

Most visits to a typical Shopify store come from phones, and phones are where upsell offers go wrong. A window that looks tidy on a laptop becomes, on a small screen, a box that covers the checkout button, a close icon too small to hit, and an image that pushes the price out of sight. The customer doesn’t read it. They look for a way out.

What goes wrong on a small screen

• The close button is a tiny cross in a corner, easy to miss and hard to tap with a thumb.
• The window is taller than the screen, so the buttons sit below the fold and the customer has to scroll inside a pop-up.
• The page behind still scrolls, and the customer loses their place.
• The window takes a second to appear, and the customer has already tapped something else.
• The offer arrives on top of the theme’s own pop-ups: newsletter, cookies, chat.

What works

• A panel that rises from the bottom of the screen, where the thumb already is, rather than a box in the middle.
• Everything visible without scrolling: a small image, the product name, the price, two buttons.
• A decline button written out in full — “No thanks, continue to checkout” — as large and easy to tap as a normal button.
• The keyboard and accessibility basics: the offer can be closed with Escape, and it respects customers who turn off animations.
• Your store’s look. A pop-up in a different font and colour from the rest of the store reads as an ad, and ads get closed.

A five-minute test on your own phone

1. Open your store on your phone, not on a laptop resized to look like one.
2. Add the product that triggers the offer to the cart and tap checkout.
3. Check that you can see the price and both buttons without scrolling.
4. Decline with your thumb, one-handed. Then try again and accept.
5. Repeat on a second phone if you can, ideally a small or older one.

Also try it with the cookie banner still open, and with your newsletter pop-up enabled. Two windows at once is the most common way a good offer gets closed without being read.

After payment, less is in your hands

The post-purchase page is drawn by Shopify, not by your theme or the app, and it is already built for phones. What you control there is the wording and the product, so the rules above still apply to what you write: a clear headline, a visible price, an obvious way to decline.

In FlatUpsell

FlatUpsell’s cart offer becomes a panel rising from the bottom of the screen on phones, with the price and both buttons in view. It picks up your theme’s font and takes the colour and corner radius of your own checkout button, closes with Escape, and skips its animation for customers who have turned animations off. You can preview it on your real cart page from the app before any customer sees it.