Shopify checkout extensions — custom checkout UI for Shopify Plus brands

Shopify checkout extensions are UI components added to the checkout through Shopify's supported Checkout Extensibility API — rather than by editing checkout.liquid directly. They let you add custom UI blocks, collect additional information from customers, display loyalty points or personalised offers, add gift messaging, and customise the checkout experience without touching core checkout code. Because they use Shopify's supported extension points, they are upgrade-safe and compatible with future Shopify changes — unlike checkout.liquid edits, which Shopify is deprecating.

Yes — checkout extensibility and checkout UI extensions require a Shopify Plus plan. Standard Shopify plans do not allow checkout customisation beyond what Shopify's native settings provide. Post-purchase extensions (thank you page and order status) are available on all plans, but in-checkout extensions require Plus.

We build the full range of checkout UI extensions: post-purchase upsells and cross-sells, custom fields for order notes, delivery preferences, and gift messages, address validation and postcode lookups, loyalty points displays and redemption, custom payment method messaging, age verification gates, and promotional offers targeted to cart contents or customer segments. We also build order status page extensions for post-purchase engagement and referral prompts.

Shopify deprecated checkout.liquid for Shopify Plus merchants in August 2024. Stores still using checkout.liquid for custom checkout UI need to migrate to checkout extensibility to maintain their customisations. The migration involves rebuilding custom checkout UI using Shopify's extension APIs — the functionality is preserved, but the implementation approach changes entirely. We manage these migrations as part of our checkout extensions work.

Yes — selectively. Upsell and cross-sell extensions at the right point in checkout can increase AOV without hurting conversion. Loyalty point displays reduce abandonment for customers who do not realise they have redeemable value. Address validation removes a common friction point that causes failed deliveries and customer service load. The key is being selective: adding too many UI elements to checkout increases cognitive load and can hurt conversion. We scope checkout extensions against a clear business objective, not as features for features' sake.

Shopify Functions are a related but separate capability — they let you customise Shopify's backend logic for discounts, payment options, delivery methods, and cart transformations. Where checkout UI extensions change what customers see in the checkout, Functions change how Shopify processes the order — running custom discount logic, filtering payment methods by cart conditions, or rewriting line items before order creation. We build both, often combined: a Function to apply custom discount logic and an extension to display it clearly in the checkout UI.

Simple single extensions — a custom field, a gift message input, or a loyalty display — typically take two to four weeks from scoping through testing and launch. More complex projects involving multiple extensions, custom backend logic with Shopify Functions, or integration with third-party loyalty or personalisation platforms take longer: usually six to ten weeks. We build in thorough QA against Shopify's checkout environment, since checkout bugs have a direct revenue impact.

Checkout extensibility is one of several Plus-only capabilities — alongside B2B, custom checkout flows, Launchpad, and higher API rate limits. If checkout customisation is your primary reason to consider Plus, we would first check whether the specific outcome you want can be achieved through checkout extensibility before recommending an upgrade, since Plus carries a significant cost increase. If the business case stacks up across multiple Plus features, the upgrade is usually worth it. See our Shopify Plus agency page for the full picture on when Plus makes sense.