Fall '26 for developers: what to fix in your theme and apps before the 2027 deadlines

The deadlines

Script tags: the one most likely to bite

Script tags were the old way for apps to inject JavaScript into your storefront: review widgets, chat, pop-ups, tracking. From 1 March 2027 Shopify won’t load them. Apps should move storefront code into an app embed block and tracking into a web pixel.

Three catches to know about:

• App embeds are switched on per theme. Publish a new theme and you need to check each embed is active on it.
• Overlap doubles up. While a script tag and its replacement both run, the script loads twice, which can double-count analytics or show a widget twice.
• Admin-created custom apps can’t use app extensions. If one injects a script, that code has to move into your theme, ideally via a custom Liquid block. If a third-party service had you create the app and paste in a token, that service needs to ship a proper app.

Expiring tokens

Public App Store apps must switch to expiring offline access tokens. Custom and merchant-created apps are excluded. Your job as a merchant is simple: when admin warnings appear in January, chase the vendor, because from April a non-compliant app stops being able to read or write your data.

Worth adopting

• Shopify Functions can now read metafields on delivery options, and soon the right metaobjects for each checkout. Bundle, delivery and eligibility rules can then be edited in the admin rather than in code.
• Checkout Kit, updated, embeds Shopify’s checkout in web, native mobile and agentic experiences.
• Admin API additions include purchase orders for ERP and inventory integrations, rollout status with webhooks, and events covering 18 topics.
• App events in analytics let apps send activity, such as loyalty points redeemed, into Shopify’s reports, and write annotations explaining what they changed.
• Shopify Flow automations can be built and managed by your preferred agent through the AI Toolkit.
• Shopify CLI now suits agents, with non-interactive input and output, dev store creation, app security checks and, soon, production log queries. Apps can also restrict API calls to allowlisted IP addresses.
• Official Python and PHP packages for building apps.

Storefronts

The new theme architecture, in developer preview, composes pages in Liquid with blocks, typed contracts and partial updates, with Tailwind built in and markdown files to guide agents. Canvas is built on it. It isn’t a reason to rebuild today, but plan your next theme on it.

Two changes help straight away. Shopify now serves only the CSS each page uses, so stores load faster with no work. And Hydrogen gains customer accounts, predictive search, agent skills and one-click Vercel deploys. For most brands under £1.5m, though, a well-built Liquid theme is still better value than going headless.

Your audit checklist

• List every installed and custom app, and ask each vendor in writing about script tags and expiring tokens.
• Check any admin-created custom app for injected scripts, and move them into the theme.
• After each migration, confirm the app embed is on in your published theme, then remove the old script tag.
• Add AGENTS.md and DESIGN.md to your theme.
• Review custom checkout logic that Functions metafields or metaobjects could make editable in the admin.

Book a theme and app audit: we’ll check every app and integration against the 2027 deadlines and fix what’s at risk.

More in our Shopify Editions Fall ’26 series

• Shopify Editions Fall ’26: what UK brands should act on
• Checkout, payments and fraud: what Fall ’26 changes before and after Black Friday
• Agentic commerce on Shopify: getting your products sold inside ChatGPT, Gemini and Claude
• Sidekick and Canvas: putting Shopify’s AI to work without losing control
• Selling from the UK to the EU and Nordics: the Fall ’26 Markets and shipping updates

Sources

• Storefront script tags
• Migrate to expiring offline access tokens before 1 January 2027