What Is a Checkout UI Extension? Plan Limits

UI means user interface, the part a shopper sees and clicks. A checkout UI extension is the visible piece of Shopify's Checkout Extensibility system. The look comes from branding settings, while logic like discounts runs through Shopify Functions.

Where Checkout UI Extensions Can Show Up

Shopify gives apps a fixed list of spots, called extension targets. The order summary, the shipping options area and the Thank you page are some of them.

Which spots you get depends on your plan. Shopify Plus stores can put extensions in the information, shipping and payment steps. Other plans only get the Thank you and order status pages. To place one, open the checkout editor under Settings, then Checkout.

Why Shopify Keeps Checkout Locked Down

Plus stores used to edit checkout code directly in a file called checkout.liquid. But that custom code could break when Shopify changed its checkout, and it could slow the page down. Shopify has since moved stores to extensions.

Each extension runs in its own sealed box, apart from the rest of the page, and can't reach out of it to change the page. It picks up your checkout's branding too, so it blends in.

Example: does a checkout add-on pay for itself?

Say 1,000 shoppers start checkout on your Plus store each month. You add a $15 care kit offer below the order summary and 30 shoppers take it. That's 30 × $15 = $450 extra.

Now say the block distracts 10 shoppers into leaving. With a $60 average order, that's 10 × $60 = $600 lost. You'd end up $150 behind, even though the add-on sold. So judge an extension by finished orders, not add-on sales alone.

Myth: An Extension Can Change Anything in Checkout

It can't. An extension only uses Shopify's own building blocks, like text, buttons and images. It has no way to inject code into the page or restyle checkout. Showing an offer is fine, but the price change comes from a Shopify discount, such as a code or a Shopify discount function.

One-click offers shown right after payment, before the Thank you page, need a different tool, a post-purchase extension.

How Growth Suite Uses Checkout Extensions

Growth Suite, our app, uses checkout extensions on Shopify Plus stores. They show a checkout offer progress bar and upsell offers inside checkout. For other ways to help shoppers finish paying, see our guide to Shopify checkout optimization.