Checkout and extensions
Checkout UI Extensions
We design and build Shopify checkout UI extensions, custom upsells, fields, banners and trust content placed exactly where Shopify's checkout allows.
Checkout UI extensions are how you add anything custom to a modern Shopify checkout. If you want an upsell, a custom field, a delivery note or a trust badge in the checkout itself, this is the supported path, and it takes real engineering to do well.
More than dropping in a block
Anyone can install an app that adds a banner. The value is in knowing which extension point actually fits your goal, how to keep the checkout fast, and how to make the extension configurable so your team is not filing a ticket every time the copy changes. That is the part we build.
Common extensions we ship
Custom fields for gift messages, VAT and tax IDs, PO numbers and delivery instructions. Upsells and cross-sells that respect what is already in the cart. Reassurance content next to the pay button. Dynamic messaging based on cart contents, customer or shipping country.
Built to pass review and last
Extensions go through Shopify’s review and run in a sandboxed runtime. We build to those constraints from the start, so what we ship is accepted, accessible, and still working after the next platform update.
What we build
Custom extension development
Purpose-built React extensions for content, upsells, custom fields and dynamic messaging at checkout.
Extension placement strategy
We map your goals to the specific checkout targets Shopify exposes, so each block earns its space.
App-block configuration
Merchant-friendly settings so your team can adjust copy and rules without a developer.
Performance and review
Fast, accessible extensions that pass Shopify review and do not slow the pay flow.
Specialist builds
The pieces of this service clients ask for by name.
Checkout Countdown Timer
A countdown or reservation timer inside the real checkout, built as a supported UI extension rather than a theme hack.
Learn moreShipping Protection at Checkout
An opt-in protection or warranty offer inside checkout, priced to your cart and paid straight into your margin.
Learn moreBlocks we ship
Drop-in checkout blocks, live on real stores — no code, no compliance headaches.
Questions, answered
- What are checkout UI extensions?
- They are Shopify's supported way to add custom content and logic to checkout using extension points Shopify defines. They replace the old checkout.liquid customizations on Shopify Plus.
- Can I add custom fields like a gift message or VAT number?
- Yes. Custom fields are one of the most common extensions we build, and we can validate them and pass the data through to the order.
- Do extensions work with my existing checkout apps?
- Usually yes. We audit what you already run so extensions complement your apps instead of competing for the same space.
Related services
Shopify Checkout Customization
Reshape the checkout with extensions, Functions and branding to lift conversion without breaking compliance.
Learn moreCheckout Countdown Timer
A countdown or reservation timer inside the real checkout, built as a supported UI extension rather than a theme hack.
Learn moreShipping Protection at Checkout
An opt-in protection or warranty offer inside checkout, priced to your cart and paid straight into your margin.
Learn morePost-Purchase Extensions
One-click upsells and custom content on the post-purchase and order status pages.
Learn moreReady to build a store worth talking about?
Tell us where your store is today and where you want it to go. We reply within two working days with a clear next step.