Shopify Scripts to Functions Migration: What Plus Merchants Need to Do Before June 2026

Your Checkout Logic Has an Expiration Date

If you're running Shopify Plus and use Scripts for checkout customization, this is the date that matters: June 30, 2026. That's when every Script stops executing. Not deprecated. Not phased out. Off.

Your tiered volume discounts, gift-with-purchase logic, shipping method filters, payment visibility rules — anything built with Scripts vanishes from your checkout on that date.

You have weeks, not months. And if you haven't started migrating, the window is closing fast.

Here are the hard dates:

• April 15, 2026: You can no longer edit or publish Scripts. If something breaks in a live Script after this date, you can't fix it — you can only replace it.
• June 30, 2026: All Scripts stop executing. Period.

Here's what catches merchants off guard: Shopify may auto-upgrade some stores. You might not get a choice in timing. If your Scripts break during a forced migration, that's a problem you own, not Shopify.

What Scripts Do (And Why You Probably Depend on Them)

If you've hired a developer to customize your checkout in the last five years, there's a good chance they built it with Scripts. Scripts are Ruby code that runs during checkout:

Line Item Scripts (the most common):

• Tiered volume discounts: "Buy 10, get 5% off; buy 25, get 10% off"
• Gift-with-purchase logic: "Free tote bag if your order is over $50"
• Bundle discounts: "Buy all three, get 20% off the set"
• Quantity-based pricing: custom per-unit cost based on order size

Shipping Scripts:

• Hide or rename shipping methods based on cart contents
• Reorder shipping options (show Express first, Standard second)
• Conditional logic: "Free shipping for VIP customers, hide certain methods by country"

Payment Scripts:

• Hide payment methods by country or customer group
• Filter by order value or cart contents
• Enforce payment rules specific to your business model

If your store runs on any of this logic, your checkout breaks on June 30 unless you've migrated.

What Replaces Scripts: Shopify Functions

Shopify Functions are the new system for custom checkout logic. They're faster and more reliable — but they work completely differently.

What Functions are:

• Code (JavaScript, TypeScript, or Rust) compiled to WebAssembly
• Deployed as part of a Shopify app, not edited in the admin
• Run in an isolated, sandboxed environment at the edge
• Execute in sub-5ms with zero cold starts

The key architectural change: Scripts mutated a shared object — you'd say "change the line item discount to 10%." Functions are explicit — you return an operation that says "apply a 10% discount to line item ID 4729." This affects how every migration is written.

Scripts vs. Functions: The Practical Breakdown

The practical impact: if your team currently edits Scripts directly in the admin, you'll need a developer — or a migration tool — to build Functions going forward.

The Migration Path (Four Steps)

Step 1: Audit Your Current Scripts

Go to Settings → Script Editor in your Shopify admin and document:

• Every active Script
• What it does (discount logic, shipping filter, payment rule)
• What business logic it encodes ("10% off for bulk orders" or "hide this payment method in Canada")
• How complex it is (simple rule vs. multi-condition logic)

Priority-sort by business impact. A broken volume discount on your top seller is more urgent than a shipping label rename.

Most Plus stores have between 2 and 8 active Scripts. If you have more than 10, you've got technical debt to address.

Step 2: Choose Your Migration Strategy

Three real options:

Option A: Hire a developer to rebuild each Script as a Function

• Cost: $1,000–$5,000+ per Script depending on complexity
• Timeline: 2–4 weeks per Script
• Best for: Complex logic, critical business rules, or if you want to own the implementation

Option B: Use apps instead of custom Functions

• Shopify and third-party developers are building Functions-powered apps for common use cases
• Cost: $30–$200/month per app
• Timeline: A few hours to install and configure
• Best for: Standard discount, shipping, or payment filtering logic

Option C: Use AI-assisted migration

• New tools audit your existing Scripts and generate Functions implementations or compatible app recommendations
• Cost: A few cents to a few dollars per audit
• Timeline: Hours, not weeks
• Best for: The 80% of Scripts that follow common patterns — volume discounts, shipping rules, payment filters

Most merchants use a hybrid: Options B and C for simple Scripts, Option A for critical custom logic.

Step 3: Test in a Development Store

Never migrate directly on your live store.

Use a Shopify development store (free for Partners) and test every scenario your Scripts currently handle:

• Real customer segments (bulk buyers, B2B accounts, loyalty members)
• Different countries and regions
• Edge cases (empty cart, one item, minimum order thresholds)
• Payment method visibility, shipping options, discount calculations
• Complete checkout flows — at least twice

The first 48 hours after go-live matter most. Watch for discount calculations that don't match, shipping options that disappear, payment methods hidden incorrectly, and any redirect issues.

Step 4: Deploy and Monitor

Roll out during low-traffic periods. Have someone monitoring checkout for at least 48 hours after deployment.

Track your conversion rate, cart abandonment rate, payment success rate, and customer support volume. If something's wrong with checkout, customers will tell you fast.

Keep the old Scripts in place until you're confident in the Functions. If you need to roll back, do it immediately.

What Actually Breaks (Learn from Other Merchants)

These are real issues Plus merchants have hit during migration:

Checkout breaks on launch day — Migration during peak traffic causes cascading failures. Always migrate during low-traffic windows (early morning, overnight, or weekend).

Analytics tracking drops — Checkout extensibility migration can break GA4 pixels and other tracking. Test analytics pings alongside checkout logic before full rollout.

B2B logic gaps — Scripts handling B2B-specific pricing or customer group filtering work differently in Functions. Test with your actual B2B account structure.

Institutional knowledge is lost — The developer who built your Scripts left two years ago. Nobody documented the business logic. Audit Scripts now, while someone still remembers what they do.

Payment method filtering doesn't match — Payment Scripts are scoped differently in Functions. Test from multiple countries and with different customer groups.

Shipping method ordering changes — The order of shipping options matters for UX. Scripts allowed arbitrary reordering; Functions handle this differently. Test from different regions.

What Happens If You Do Nothing

This needs to be said clearly: if you don't migrate by June 30, your checkout loses every custom rule built with Scripts.

That means your volume discounts stop applying. Your gift-with-purchase logic disappears. Your shipping method filters turn off. Your payment visibility rules vanish. Customers see a default checkout with none of the custom behavior you've built over years.

For most Plus stores, that translates directly to lost revenue. A merchant running tiered B2B pricing through Scripts loses their entire pricing structure overnight.

Don't wait.

AI-Assisted Migration: The Fastest Path for Common Scripts

For the 80% of Scripts that follow common patterns, AI-assisted migration is the fastest and cheapest option. Here's how it works:

• You describe what your Script does — or paste the code directly
• An AI agent audits the logic and maps it to Functions equivalents
• You get an implementation plan: which Scripts can become native Functions, which are better served by existing apps, and which need custom development
• Simple Scripts get migrated in minutes. Complex ones get a detailed spec for a developer.

Juvant AI is building migration skills specifically for this workflow — a Scripts Migration Auditor that reads your existing code and produces a Functions migration plan, plus a Checkout Extensibility Checker that identifies compatibility issues before you start. These run on demand: a few cents per audit, no monthly subscription, no app install.

For merchants with 2–5 simple Scripts, this approach can handle the full migration in an afternoon. For stores with complex multi-condition logic, it handles the easy Scripts and gives your developer a head start on the hard ones.

Timeline: Your Action Plan

The clock is ticking. Here's what to do and when:

• This week: Audit all active Scripts. Document what they do. 30 minutes.
• Next 2 weeks: Sort by complexity. Identify critical vs. nice-to-have.
• Weeks 3–5: Migrate the simplest Scripts using apps or AI-assisted tools. Test in a dev store.
• Weeks 5–8: Tackle complex Scripts. Bring in a developer or use an AI migration tool for the implementation spec.
• Before June 30: Full migration complete. Tested on live. Monitored. Done.

You don't need to do everything this week. But you do need to start. The merchants who wait until June are going to face developer backlogs, rushed testing, and broken checkouts.

Audit your Scripts → Try the migration auditor free