Shopify’s Checkout Extensibility represents a significant shift for e-commerce businesses, offering a more secure, upgrade-safe, and high-performing checkout experience. This new approach removes the ability to modify checkout.liquid directly, instead requiring businesses to use Shopify Functions, Checkout UI Extensions, and the Branding API for customisations. While this change promises long-term benefits, it also introduces several challenges, particularly for Shopify Plus merchants who have relied on deep checkout customisations.

With Shopify planning to fully deprecate checkout.liquid by August 2025, businesses that rely on advanced checkout modifications must start preparing for the transition now. However, this is not a simple upgrade—it requires a complete shift in how merchants approach checkout customisation. Below, we explore the key challenges associated with Shopify Checkout Extensibility and discuss possible solutions.

The End of checkout.liquid and the Loss of Direct Customisation

One of the biggest challenges is the complete removal of checkout.liquid. For years, Shopify Plus merchants have used checkout.liquid to implement a wide range of checkout customisations, from personalised upsells and dynamic forms to bespoke styling and unique payment flows. The flexibility of Liquid allowed merchants to tailor the checkout experience to their exact needs, offering a distinct advantage over competitors.

Now, all modifications must be done using Checkout UI Extensions and Shopify Functions, which operate within a predefined structure dictated by Shopify. This means that some previously simple customisations—such as adding custom fields, modifying the checkout flow, or embedding trust badges—may now require workarounds or third-party apps. For businesses that have invested heavily in custom checkout solutions, this transition could be both costly and time-consuming.

To mitigate these challenges, Shopify encourages merchants to use its Checkout UI Extensions, which provide predefined extension points for inserting content, modifying layouts, and adding interactive elements. However, these extension points do not yet offer the same level of flexibility as checkout.liquid, meaning that some businesses may need to compromise on their original vision. For merchants with complex needs, working with a Shopify Plus Partner or experienced developers may be necessary to find suitable solutions.

Key Takeaways:

• Shopify is removing checkout.liquid, meaning merchants must use Checkout UI Extensions and Shopify Functions for customisation.
• Some previously simple modifications now require workarounds or third-party apps.
• The level of flexibility is currently more limited than before, potentially requiring businesses to rethink their checkout experience.

Limited Checkout UI Extensions and Customisation Restrictions

While Checkout UI Extensions offer a more structured and upgrade-safe way to modify the checkout experience, they come with significant limitations. Unlike checkout.liquid, where developers had full control over the checkout layout, Shopify now dictates where and how modifications can be applied. This can be frustrating for businesses that require unique checkout flows, such as multi-step processes, conditional form fields, or advanced upsell placements.

One key issue is that extension points are predefined, meaning merchants cannot freely position custom elements anywhere they choose. For example, if a business wants to add an interactive shipping calculator or a loyalty rewards prompt at a specific stage of checkout, they may find that the available extension points do not accommodate their needs. This limitation makes it difficult to create fully bespoke checkout experiences.

The best way to work around this challenge is to keep an eye on Shopify’s ongoing updates, as new extension points are expected to be introduced over time. Additionally, merchants should work closely with Shopify developers to explore creative solutions within the existing framework. In some cases, integrating third-party apps or embedding content dynamically via Shopify’s Branding API can help bridge the gaps in functionality.

Key Takeaways:

• Checkout UI Extensions limit where and how merchants can modify checkout.
• Predefined extension points restrict the ability to freely place elements.
• Businesses should monitor Shopify updates and work with developers for solutions.

Shopify Functions Replace Shopify Scripts—But With Limitations

Another major change with Checkout Extensibility is the introduction of Shopify Functions, which replace Shopify Scripts for controlling discounts, payment methods, and shipping rates. While Shopify Functions offer a more scalable and API-driven approach to checkout logic, they come with several restrictions that could pose challenges for merchants with advanced requirements.

For instance, Shopify Functions currently only support discounts, shipping rules, and payment customisations. This means that certain advanced checkout logic—such as cart-level validations, bundle-specific pricing rules, or tiered discount structures—may not be possible without relying on external apps.

Key Takeaways:

• Shopify Functions replace Shopify Scripts, but their capabilities are currently limited.
• Businesses that require advanced checkout logic may need third-party apps.
• Shopify is expected to expand Functions capabilities over time.

Third-Party App Compatibility and Migration Challenges

Many checkout-related apps—such as upsell tools, loyalty programme integrations, or custom payment gateways—were built on checkout.liquid and may no longer function as expected.

Many app developers are updating their solutions, but merchants should check with providers to confirm compatibility. Shopify’s App Store also has new apps that support Checkout Extensibility, but some businesses may need to invest in custom development to replace missing functionality.

Key Takeaways:

• Some third-party apps built for checkout.liquid may no longer work.
• Merchants should check app compatibility and explore alternative solutions.
• Custom development may be needed for missing functionality.

Increased Complexity and a Steep Learning Curve

Shopify’s new approach relies on Shopify Functions, UI Extensions (React-based), and APIs, meaning that businesses may need to invest in new technical expertise or hire developers.

Testing and debugging have also become more complex, as merchants no longer have direct access to checkout code. Instead, they must work within Shopify’s controlled environment, using Shopify CLI and developer tools to preview changes.

Key Takeaways:

• Businesses need to learn new technologies or hire developers.
• Debugging and testing are more complex due to Shopify’s controlled environment.
• Using Shopify CLI is essential for testing changes.

The Urgency of Migration: Mandatory Adoption by August 2025

By August 2025, Shopify will fully deprecate checkout.liquid, meaning all businesses must transition to Checkout Extensibility or risk losing their checkout customisations.

For businesses with highly customised checkouts, the time to act is now. Delaying the transition could result in last-minute disruptions, rushed implementations, and potential revenue loss if key checkout functionality is not properly migrated.

Key Takeaways:

• Shopify will fully deprecate checkout.liquid by August 2025.
• Businesses must migrate to Checkout Extensibility to avoid losing customisations.
• Early preparation is key to a smooth transition.

Final Thoughts

Shopify Checkout Extensibility brings many benefits, including better performance, improved security, and long-term sustainability. However, for e-commerce businesses that have relied on highly customised checkout experiences, the transition presents significant challenges that must be carefully navigated.

With the August 2025 deadline looming, businesses should audit their checkout setup, explore available extension points, and start planning their migration strategy now. While the process will require effort, those who adapt early will be in a stronger position to innovate and future-proof their e-commerce operations