Checkout is the part of an eCommerce platform that gets the most attention and the most customization pressure. Conversion teams want A/B tests. Operations teams want shipping rule complexity. Finance teams want tax accuracy across jurisdictions. Marketing teams want upsell modules. The platform’s ability to handle these requests without breaking is one of the most important factors in long-term platform fit. The conversation about Shopify Plus checkout extensibility versus Adobe Commerce checkout has changed substantially in 2026, and the right comparison today looks different than it did even eighteen months ago.
This piece walks through the current state of both platforms’ checkout customization surfaces. It is written for engineering leaders, eCommerce directors, and CTOs evaluating which platform their business should run on, particularly those reconsidering the decision in light of Shopify’s checkout extensibility maturity and Adobe Commerce’s recent updates. The patterns below come from Bemeir’s work building and maintaining checkouts on both platforms.
Shopify Plus Checkout Extensibility: Where It Stands in 2026
Shopify’s checkout architecture has gone through a significant evolution. The legacy Checkout.liquid customization model, which allowed merchants to modify checkout templates directly, has been deprecated for new development and will be fully sunset in 2026. The replacement is Checkout Extensibility, built on Shopify Functions and Checkout UI Extensions, which is a fundamentally different architectural model.
Checkout Extensibility provides:
- Checkout UI Extensions: React-based components that render in defined extension points within the checkout flow
- Shopify Functions: WebAssembly-compiled logic that runs server-side to modify cart, shipping, payment, and discount behavior
- Branding API: declarative configuration for visual customization of the checkout
- Customer Account Extensibility: similar patterns extended to the customer account area
- Headless checkout via the Storefront API and the new Checkout Kit for fully custom presentations
The constraint is that the customization happens within Shopify’s checkout shell. Merchants cannot replace the checkout entirely without going to a headless implementation, and even headless implementations route through Shopify’s payment and fraud infrastructure.
The benefit is reliability and performance. Shopify’s checkout shell is one of the most performant checkout experiences in the industry, with checkout conversion rates that consistently outperform alternative platforms in head-to-head comparisons. The trade-off is reduced flexibility in exchange for higher baseline performance.
Adobe Commerce Checkout: Where It Stands in 2026
Adobe Commerce’s checkout is more open-ended. The default checkout, built on Knockout.js historically, now supplemented by the Hyvä Checkout option, runs as standard Magento templates within the merchant’s own codebase. Anything is customizable, which means everything can be customized poorly.
Adobe Commerce checkout customization surface includes:
- Direct template modification for any element of the checkout UI
- Custom payment methods via the Adobe Commerce Payments Gateway interface
- Custom shipping methods via the carriers framework
- Custom tax calculation via the tax framework
- Custom checkout steps via the checkout flow configuration
- Hyvä Checkout for performance-optimized modern checkout (Alpine.js, Tailwind, fast)
- Headless checkout via GraphQL and the Adobe Commerce REST API
The benefit is total flexibility. The merchant can build literally any checkout flow they can imagine. The trade-off is that the merchant owns the performance, security, and reliability of the checkout. There is no Shopify-equivalent shell that handles those concerns by default.
| Capability | Shopify Plus 2026 | Adobe Commerce 2026 |
|---|---|---|
| Default checkout performance | Industry-leading, baseline | Baseline good with Hyvä, variable otherwise |
| UI customization surface | Defined extension points | Anywhere in the checkout |
| Custom payment method | App-based with platform fraud | Direct integration, merchant owns fraud |
| Custom shipping logic | Shopify Functions | Direct PHP via carriers framework |
| Custom tax calculation | Shopify Functions or app | Direct PHP via tax framework |
| Checkout flow modification | Limited to extension points | Full customization possible |
| Headless option | Storefront API + Checkout Kit | GraphQL + REST API |
| Conversion benchmark | Strong out of the box | Depends heavily on implementation |
| Customization durability | High (Shopify maintains the shell) | Depends on team discipline |
| Vendor lock-in | Higher (Shopify-owned infra) | Lower (merchant-owned codebase) |
The Customization Surface Question
The substantive question is “how customized does your checkout need to be.” Most merchants think their checkout is more customized than it actually is. In practice, the customizations that genuinely matter for business outcomes are usually:
- Custom payment methods specific to the merchant’s payment strategy
- Custom shipping logic for the merchant’s fulfillment model
- Custom tax handling for complex jurisdictions
- Upsell and cross-sell components
- Promo code and discount logic
- B2B-specific flows (PO orders, net terms, account hierarchy)
- Loyalty program integration
- Custom data capture during checkout
Shopify Plus Checkout Extensibility handles all of these. The question is whether the extension points and Function APIs cover the specific behaviors the merchant needs. For most DTC and mid-market retail, the answer is yes. For complex B2B with deep ERP integration and unusual payment flows, the answer is sometimes no.
Adobe Commerce checkout handles all of these straightforwardly because anything is customizable. The question is whether the customization burden is sustainable for the merchant’s team.
B2B Checkout: Where Adobe Commerce Still Wins
For complex B2B scenarios, Adobe Commerce continues to have an advantage in 2026. The B2B feature set, quote requests, customer-specific catalogs, shared catalogs, customer-specific pricing, multi-buyer account hierarchies, custom approval flows, PO-based ordering, is deeply integrated with the checkout in a way that Shopify Plus B2B is still building toward.
Shopify Plus B2B has made significant progress, including Company Profiles, Catalogs, and B2B-specific checkout flows. For mid-complexity B2B, Shopify Plus B2B is now viable. For high-complexity B2B with deep ERP integration and unusual approval flows, Adobe Commerce remains the safer choice.
Bemeir’s Adobe Commerce B2B practice and Shopify Plus practice both maintain dedicated B2B engineering capability, and the recommendation to clients on which platform fits varies case-by-case based on the specific B2B requirements.
Headless Checkout on Both Platforms
Headless checkout has matured on both platforms. Shopify’s Checkout Kit lets merchants present a fully custom checkout UI while routing the underlying transaction through Shopify’s secure payment infrastructure. Adobe Commerce’s GraphQL coverage now supports the equivalent pattern, with custom storefronts presenting checkout while calling Adobe Commerce APIs.
The headless option is attractive when the merchant wants a fully branded checkout experience that doesn’t match either platform’s default visual model, or when the merchant wants checkout embedded in a non-eCommerce experience (a video player, an editorial site, a mobile app). Both platforms support this in 2026.
The trade-off is engineering investment. A headless checkout is a serious build that requires ongoing maintenance. Most merchants who consider headless underestimate the ongoing cost.
Performance Comparison
Shopify’s hosted checkout is consistently fast. The checkout shell runs on Shopify’s infrastructure, optimized over a decade of conversion testing, with global CDN coverage. Most Shopify Plus merchants don’t need to think about checkout performance, it just works.
Adobe Commerce checkout performance varies. The default Knockout-based checkout is no longer recommended for new builds; new Adobe Commerce projects should default to Hyvä Checkout, which is dramatically faster and uses modern frontend patterns. Existing stores on the legacy checkout should plan to migrate to Hyvä Checkout as part of their next major performance investment.
Industry benchmarks from Baymard Institute’s checkout UX research and Shopify’s own Black Friday performance reports provide concrete numbers, but the directional pattern is clear: Shopify’s hosted checkout is the performance baseline that Adobe Commerce stores need active engineering to match.
Lock-In Considerations
Shopify Plus locks the merchant into Shopify’s payment, fraud, and checkout infrastructure. Moving away from Shopify Plus means rebuilding all three. The lock-in is real, and the merchant should be comfortable with the long-term commitment.
Adobe Commerce keeps payment, fraud, and checkout under the merchant’s control. The merchant can change payment providers, fraud tools, and checkout implementations without changing platforms. The flexibility comes with operational responsibility, the merchant has to actively maintain those layers.
For merchants evaluating long-term commitment, the lock-in question is one of the most important factors. Shopify Plus is a tighter integration with higher baseline quality. Adobe Commerce is looser coupling with more merchant control.
What Decides the Choice
The platform decision rarely comes down to checkout alone, but checkout is often where the trade-offs become most concrete. The pattern that holds:
- DTC and mid-market retail with modest customization: Shopify Plus often wins on speed-to-value and baseline checkout quality
- Complex B2B with deep ERP integration: Adobe Commerce often wins on flexibility and B2B feature depth
- Multi-storefront international with complex tax: Adobe Commerce often wins on multi-store architecture
- Headless or composable architectures: Both platforms support it; Adobe Commerce gives more control, Shopify gives more simplicity
- Limited in-house engineering: Shopify Plus reduces ongoing operational burden
- Strong in-house engineering willing to maintain customization: Adobe Commerce offers more headroom
Bemeir’s practice across both platforms, Adobe Commerce and Shopify Plus, recommends the platform that fits the merchant’s organizational capacity and strategic direction, not the platform that’s easier for the agency to deliver on. Both platforms ship excellent checkouts in 2026 when implemented well. The right choice is the one whose constraints and strengths align with the merchant’s reality.
For broader platform analysis, Gartner’s Magic Quadrant for Digital Commerce and Forrester’s Wave for B2B Commerce cover both platforms with vendor-neutral assessments. The checkout differences described above are one input into a larger decision, but they’re an important one because they determine the durability of the choice across the next several years of platform evolution.
