Short answer
Shopify Checkout Extensibility is the model for customizing the Shopify checkout not by editing code but with upgrade-safe building blocks such as app extensions (Checkout UI extensions), Shopify Functions, branding settings and web pixels. The old checkout.liquid file stopped working for the information, shipping and payment steps on Plus stores on August 13, 2024; for checkout.liquid and additional scripts on the thank you and order status pages, the deadline was August 28, 2025 for Plus stores and August 26, 2026 for other plans.
In short, as of late 2026, Checkout Extensibility is the only way to customize the checkout on Shopify. Simple customizations with ready-made apps take a few days; custom extension development for Turkey-specific fields (Turkish ID and tax numbers, KVKK consent, delivery date) takes 2–6 weeks.
This guide was prepared with the field experience of the Byte Digital team, a Shopify Plus Partner that has served Shopify brands for 7 years.
What happened to checkout.liquid? Key dates
checkout.liquid is no longer supported; all checkout customizations must move to Checkout Extensibility building blocks. According to Shopify’s developer documentation, checkout.liquid is unsupported for the information, shipping and payment steps and has also been sunset on the thank you and order status pages (Shopify checkout.liquid).
Date | What changed | Who it affected |
|---|---|---|
August 13, 2024 | checkout.liquid customizations stopped working on the information, shipping and payment steps | Shopify Plus stores |
August 28, 2025 | checkout.liquid, additional scripts and script tags were sunset on the thank you and order status pages; the additional scripts field became read-only | Shopify Plus stores |
June 30, 2026 | Shopify Scripts stopped executing entirely (editing had closed on April 15, 2026) | Plus stores using Scripts |
August 26, 2026 | Deadline to upgrade the thank you and order status pages to the new version | Plans other than Plus |
Conversion codes, survey tools or custom messages added to the thank you page in the old setup must now be rebuilt with extensions and web pixels. We covered moving tracking codes to the new setup in detail in our Shopify server-side tracking and Consent Mode post.
Checkout Extensibility building blocks and plan differences
Checkout Extensibility consists of four main building blocks, and the most important plan difference is this: placing extensions on the information, shipping and payment steps is only possible on Shopify Plus, while the thank you and order status pages can be customized on all plans except Starter. For a current summary of plan differences, see Shopify’s technologies page (Shopify checkout technologies).
Building block | What it does | Plan |
|---|---|---|
Checkout UI extensions (information, shipping, payment steps) | Adds components such as fields, checkboxes, banners and product offers to the checkout | Shopify Plus only |
Checkout UI extensions (thank you and order status) | Adds blocks such as surveys, info boxes and shipping details to post-purchase pages | All plans except Starter |
Shopify Functions | Server-side logic such as discounts, hiding/reordering payment and delivery methods, cart and checkout validation | All plans except Starter via App Store apps; custom apps containing Functions are Plus only |
Checkout branding (Admin API) | Detailed visual settings such as colors, fonts and corner radius | Shopify Plus only |
Web pixel extensions | Tracks customer events during and after checkout | All plans except Starter |
In practice this means: a non-Plus store can use Functions-based App Store apps for custom discount rules or hiding payment methods, but cannot add a custom Turkish ID field to the payment step. Plus stores can customize every step with their own custom apps. Extensions work with Shopify’s UI components and have a bundle size limit (64 KB), so free-form HTML or heavy scripts cannot run on the checkout.
Use cases for stores in Turkey
In Turkish Shopify stores, Checkout Extensibility is used most to collect e-invoice details, obtain legal consents and adjust payment and delivery options to local rules.
Turkish ID / tax number and e-invoice fields (Plus): Individual or corporate invoice choice, Turkish ID number (TCKN), tax number (VKN) and tax office fields are added to the information step; values are written to an order metafield, and the ERP or e-invoice integration reads them from there. On non-Plus stores this information is usually collected on the cart page.
Format validation: A cart and checkout validation function can block progress to payment until an 11-digit TCKN or a 10-digit VKN is entered.
KVKK notice and explicit consent checkbox (Plus): A link to the privacy notice and a separate explicit consent checkbox can be added to the checkout; for marketing permission, Shopify’s own email and SMS consent fields should be used. For the legal side, see our KVKK and ETBİS compliance guide.
Gift note and wrapping option (Plus): Moving the gift note field and gift wrap choice to the checkout reduces notes forgotten on the cart page.
Delivery date selection (Plus): As in Shopify’s official example, a date picker can be shown when a specific shipping option is selected, and the chosen date is written to an order metafield.
Payment method rules (all plans, via an app): Hiding cash on delivery above a certain basket amount or reordering payment methods is done with Functions. For the card payment side, see our Shopify iyzico integration and Shopify virtual POS setup posts.
Thank you page (all plans): Shipping time information, a WhatsApp support link, a survey or a discount code for the next order can be shown.
Moving to and customizing Checkout Extensibility step by step
A customization with ready-made apps takes 3–5 business days; Plus projects that need custom extension development take 2–6 weeks.
Inventory (1–2 days): All customizations on the checkout and thank you page, additional scripts, tracking codes and any Shopify Scripts are listed. The upgrade report in the Shopify admin guides this step.
Mapping (1–2 days): A replacement is chosen for each customization: a ready-made app, a Checkout UI extension, a Function, a web pixel, or no longer needed.
Installing ready-made apps (1–3 days): App Store apps are installed and blocks are placed in the checkout editor.
Custom development (1–4 weeks, if needed): A custom app is built for Turkish ID and tax number fields, KVKK consent, validation functions and data transfer to the ERP.
Moving tracking codes (2–3 days): Conversion codes in additional scripts are moved to web pixels or server-side tracking, and Consent Mode settings are verified.
Testing and launch (2–3 days): The new setup goes live after testing different payment methods, mobile devices, discounted baskets and individual and corporate invoice scenarios.
The main cost factors: whether the store is on Plus, the number of custom fields and validations, transferring data to the ERP or e-invoice system, the number of tracking codes to move and the complexity of logic moving from Shopify Scripts to Functions.
The 6 most common mistakes with Shopify Checkout Extensibility
Most mistakes in Checkout Extensibility projects come from trying to copy old customizations one to one and from not testing the data flow end to end.
Forgetting tracking codes on the thank you page: When additional scripts are removed, conversion measurement silently stops and ad performance appears to drop.
Assuming Plus-only features are open to every plan: Information, shipping and payment step extensions do not work outside Plus; the project plan must reflect this.
Not writing collected data to the order: If a Turkish ID number or delivery date is collected at checkout but not written correctly to a metafield, the ERP and e-invoice side cannot see it.
Skipping format validation: Missing or wrong TCKN/VKN values lead to rejections and manual corrections when issuing e-invoices.
Filling the checkout with unnecessary blocks: Every extra field can affect conversion rate; only legally or operationally required fields should be added.
Not testing on mobile: Since most payments come from mobile, extensions should be tested separately on small screens and with different payment methods.
Shopify Checkout Extensibility with Byte Digital
Byte Digital is an Istanbul-based Shopify Plus Partner and has provided Shopify setup, migration and integration services to leading Turkish brands for 7 years. In Checkout Extensibility projects we manage the process from the inventory of existing customizations to Turkish ID and tax number fields, KVKK consent and Functions development, and after launch our Shopify technical support team monitors the health of the checkout.
Share your current plan, the fields you need at checkout and the ERP or e-invoice system you use; we will prepare a free pre-assessment with the right solution, timeline and estimated budget for you.
Request a free Checkout Extensibility pre-assessment →
Frequently asked questions
Can checkout.liquid still be used?
No. checkout.liquid is unsupported on the information, shipping and payment steps, and on the thank you and order status pages it was retired as of August 28, 2025 for Plus and August 26, 2026 for other plans.
Is Checkout Extensibility only for Shopify Plus?
No. Thank you and order status page extensions, App Store apps containing Functions and web pixels can be used on all plans except Starter. Placing extensions on the information, shipping and payment steps, however, is only possible on Plus.
Can a Turkish ID number field be added to the Shopify checkout?
On Shopify Plus stores it can be added with a Checkout UI extension, and the value is written to an order metafield. On non-Plus stores this information is usually collected on the cart page.
What replaces Shopify Scripts?
Shopify Scripts stopped executing entirely on June 30, 2026. Discount, payment and delivery method logic is now built with Shopify Functions.
Where do conversion codes on the thank you page move to?
Codes in additional scripts move to web pixel extensions (customer events) or server-side tracking. Ad platforms’ official Shopify apps cover most of these events with their own pixels.
Can free-form HTML or JavaScript run on the checkout?
No. Checkout UI extensions work with Shopify’s UI components and run in a secure environment. This restriction exists to protect the speed and security of the checkout.
