Checkout Extensibility replaces checkout.liquid and brings you more stability, security, and better upgradeability – but with clearly defined technical constraints. The good news: What’s possible works reliably and is future-proof.
For Swiss Shopify Plus merchants (because only Plus provides access to these features), this specifically means: You can selectively extend your checkout, but not customize it arbitrarily. Those who know the limitations plan realistically and save themselves expensive experiments.
If you first want to know what Shopify Checkout Extensibility actually is and when it’s used, check out our earlier article.
The Hard Technical Limits – What Really Doesn’t Work
Checkout Extensions bring stability and update security, but they set clear boundaries. What used to be possible with checkout.liquid is often deliberately excluded today.
- No custom code: HTML, CSS, or JavaScript in the checkout are off-limits. Customizations only work through Shopify’s designated UI components.
- Fixed structure: The order of checkout steps is unchangeable. Fields and blocks only fit in predefined positions; a completely new layout is out of the question.
- Limited payment logic: Payment providers can be sorted in the admin, but not dynamically controlled via code. You can’t directly attach custom fees or conditions to payment methods.
- No direct changes to cart or prices: Line items, quantities, and prices are write-protected in the checkout. Adjustments must be made beforehand in the cart or via Functions.
- Limited additional fields: Only simple inputs or checkboxes in designated spots. More complex data collection needs apps or workarounds.
- No custom tracking or scripting: Third-party tags or A/B tests aren’t allowed to run directly in the checkout. Tracking must go through Shopify Payments and the official pixel infrastructure.
- Shipping logic not customizable: Neither sorting nor dynamic display (e.g., “Free shipping over 100 francs”) is directly possible – that goes through Shopify Functions or Carrier Services.
- Discounts API not fully integrated: Discounts must be handled via Functions or app layer, no direct access from Extensions.
In short, Shopify sets a clear framework in which the checkout functions. In return, it runs stable, update-proof, and identically on every device.
Swiss Requirements in Checkout
For Swiss shops, there aren’t any special limitations that don’t also apply internationally. TWINT has been directly integrated via Shopify Payments since 2025, and QR invoices can be integrated via apps. However, you should keep these Switzerland-specific configurations in mind:
- VAT rates: As of 2024, rates are 8.1% (normal), 2.6% (reduced), and 3.8% (accommodation). These must be correctly configured in the Shopify backend, since Checkout Extensions don’t allow overrides.
- B2B sales abroad: With the reverse-charge procedure, no Swiss VAT is charged. This must be cleanly configured in tax settings, otherwise incorrect invoices are at risk.
- UID fields for B2B: Swiss B2B customers often need UID or VAT fields in checkout that aren’t natively available. This only works via apps or custom Functions.
- QR invoices: Not natively available, but apps like Sufio or custom developments cover this – usually with ERP integration.
The most important local requirements – VAT display, multilingual content, invoice payment – are achievable with standard means.
Compliance and Legal Requirements
Legal requirements in Swiss e-commerce resemble those of the EU, but aren’t identical. There’s no uniform legal regulation like the EU Consumer Rights Directive.
Important differences from the EU:
- Price Indication Ordinance (PAngV-CH): All final prices must be shown including VAT and any surcharges. Shopify handles this automatically, but special cases like EU deliveries with foreign VAT need manual checking.
- Cookie banners: Swiss data protection law is less restrictive than GDPR. Still, a banner makes sense with international traffic – especially if you also sell to Germany or Austria.
- Terms and right of withdrawal: There’s no general right of withdrawal like in the EU, but there is a transparency requirement. The link to terms should be clearly visible, which Shopify fulfills by default.
- Payment methods: TWINT, PostFinance, and buy on account have their own legal requirements. With buy on account, mandatory information must be on the invoice – usually handled by apps or ERP integrations.
In practice, this means: Swiss merchants have somewhat more freedom in checkout design, but must carefully check which information is needed for final price, VAT, and contract conclusion.
App Dependency and Its Cost Traps
With Checkout Extensibility, much of what was once solved directly in code shifts into the app sphere. This sounds convenient but quickly leads to dependencies and ongoing costs.
Many requirements – like additional input fields, special terms checkboxes, or B2B logic – can now only be implemented via third-party apps.
Typical cost traps:
- Additional fields: Custom Fields Plus or Checkout Blocks cost CHF 10–30 monthly – what used to be a few lines of code.
- Gift options: Usually with fees per order – with high volume, this adds up.
- B2B functions: Net/gross price switching or customer tags are often only achievable with Plus apps or custom Functions.
Add to this that multiple checkout apps can block each other or slow loading time.
Especially for shops with individual checkout flows, a careful review is worthwhile: Which functions are truly business-critical? Sometimes a Function or clever workaround via the theme is enough.
The strategic combination of native features, targeted apps, and custom developments saves money long-term.
Migration from checkout.liquid – What You Need to Know
You can’t really speak of a true “migration” anymore – checkout.liquid is history. Since 2024, Shopify no longer picks up individual checkout customizations from the old Liquid architecture.
Even if the code is still present, it won’t be executed at checkout. For merchants, this means: There’s nothing to actively migrate – old customizations simply don’t work anymore.
Our experience: Many merchants had poorly documented old checkout customizations. Catching up on an overview saves a lot of effort in rebuilding and prevents important features from being overlooked.
Early testing is crucial. Many merchants only notice after weeks that old validations, discounts, or shipping notices are missing – then the damage is often already done.
Best Practices from Agency Experience
Anyone wanting to successfully deploy Checkout Extensibility should plan realistically from the start.
The following points have proven decisive:
- Check business-critical features first: B2B fields, UID numbers, gift options, or terms checkboxes – what’s truly necessary should be specifically replaced via Extension or app. Everything else can wait or be dropped entirely.
- Simplicity pays off: Those who avoid unnecessary special logic benefit from better stability, performance, and maintainability. Less is often more – especially in checkout.
- Test early: A structured test of all checkout scenarios prevents unpleasant surprises.
- Catch up on documentation: Old checkout customizations were often poorly documented. An overview saves much effort in rebuilding and also helps new team members.
- Approach app selection strategically: Not every function needs its own app. Too many apps slow down checkout and increase ongoing costs.
The Future of Checkout Extensibility
Shopify is investing massively in Checkout Extensibility – and it shows. Since 2023, new API extensions, UI components, and Functions types have been added almost monthly.
The trend is clear: more flexibility, but within clear boundaries.
Shopify is working on:
- Extended API coverage: Even more fields and validations should be mappable without endangering stability
- New Extension Points: Such as for promotions, cross-selling in checkout, or post-purchase upsells
- More control over the post-purchase flow: Including up- and cross-sells directly after the order
- Better developer tools: UI Extensions should be faster to test and set up
Long-term, checkout will become a modular platform: Merchants add functions like building blocks instead of developing them themselves. This increases update security and reduces maintenance costs.
The future is clearly API- and component-based. Those who accept this early and restructure their processes accordingly benefit from more stability and lower operating costs.
Conclusion: Realistic Expectations Lead to Success
Checkout Extensibility is a solid, future-proof solution – but not a silver bullet. Those who know and accept the technical limitations plan realistically and save themselves expensive experiments.
The most important insight: What’s possible works reliably. What’s not possible can often be solved via apps, Functions, or clever workarounds.
For Swiss shops: Most local requirements (TWINT, VAT, multilingualism, QR invoices) are achievable with standard means. Special B2B requirements often need individual solutions, but these are feasible with Shopify Plus.
If you need support with planning or implementing Checkout Extensibility, an experienced Shopify agency can help. We know the pitfalls from hundreds of projects and can show you which customizations make sense for your business model.