What You Can Actually Do with Shopify Plus Checkout

Checkout is where the money is made or lost. It is also the one part of Shopify that used to be locked down. That changed with Checkout Extensibility, which gave Plus merchants real control over the checkout experience without touching fragile Liquid code.

Here is what you can actually build on Shopify Plus today, why it matters for conversion, and where we have seen the biggest wins for our clients.

Checkout Extensibility, Functions, and Branding API

Three features do most of the heavy lifting.

Checkout Extensibility is an app based framework that lets developers add UI blocks at defined points in the checkout. No more checkout.liquid. Everything is upgrade safe, which means Shopify can release new checkout features without breaking your customizations.

Shopify Functions let developers write server side logic that runs on Shopify’s edge network with zero latency. Discounts, shipping rules, payment method controls, cart validation, all of it runs instantly at checkout. Functions replace Shopify Scripts fully by June 30, 2026, so any store still on Scripts needs to plan a migration.

The Branding API gives developers programmatic control over checkout styling, fonts, colours, and trust elements, which is especially useful for Plus merchants managing multiple storefronts or international markets.

Common customizations that move the needle

Not every brand needs every bell and whistle. These are the customizations we see pay off the most.

• Custom fields. Delivery notes, gift messages, VAT or business numbers, age verification, project references for B2B orders.
• Conditional delivery options. Show local delivery only within certain postal codes, hide express shipping on fragile items, surface free shipping thresholds.
• Loyalty at checkout. Let customers redeem points or see their tier benefits directly in the flow, rather than buried in their account.
• Upsells and order bumps. Pre purchase offers through checkout UI extensions, or post purchase offers after payment but before the thank you page.
• Payment method control. Hide specific gateways by region, product type, or customer tag using Functions.
• Trust signals. Security badges, shipping guarantees, and policy links placed at the exact moment a customer is deciding whether to complete.

What impact actually looks like

Shopify cites a 1 percent average conversion lift from Checkout Extensibility on its own. Shop Pay, which comes along for the ride, converts up to 50 percent better than guest checkout. In our own work with Plus merchants we have seen checkout customizations lift conversion by 10 to 30 percent when paired with a proper UX review.

The honest take is that checkout customization is not a silver bullet. It is a multiplier. If your product pages are weak, a great checkout will not save you. But if you already have demand and you are leaking revenue at the final step, this is where the money is.

How port80 approaches it

We start with the data. Before we touch checkout we look at abandonment rates, drop off by step, and device split. Then we map the customer’s actual friction points, not assumed ones. From there we design and build against those specific problems, usually some combination of checkout blocks, Functions, and a branding refresh.

As a Shopify Premier Partner we have built custom checkouts for fashion brands, regulated goods merchants, B2B distributors, and subscription companies. Every one of them needed something different.

If you are on Plus and still running a default or checkout.liquid setup, you are leaving both conversion and compliance on the table. The upgrade is not optional, and the opportunity is real.