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Shopify Functions Developers and Scripts Migration

Shopify Scripts stopped running on 30 June 2026. If your store used them for tiered discounts, hidden shipping rates or payment rules, that logic is gone, and a Shopify Functions developer is the person who rebuilds it.

Functions are small pieces of code that run on Shopify's servers during cart and checkout, deciding discounts, delivery options, payment methods, bundles and validation. Packaged in a public app, they work on any plan; built as a custom app for your store alone, they need Shopify Plus. For the background, read Shopify Functions explained.

This service is the logic, not the look. Blocks and messages on the checkout page are checkout UI extensions, and broader decisions about what your checkout should do sit with checkout customization. Compare the nine developers below, or request a quote with a plain list of the rules you need.

Top-rated Shopify Functions developers

What to check before hiring a Functions developer

Most Functions briefs are a handful of rules, but each rule touches every order. Hire for precise rule-writing as much as for code.

Ask whether a native discount or an app covers it first. Shopify's own discounts handle percentage and fixed-amount offers, buy X get Y and free shipping, and can be set to combine. Public apps built on Functions cover many common patterns on any plan. A developer who checks this before quoting is saving you money.

Confirm your plan before the quote. A custom app containing Functions, built for your store alone, needs Shopify Plus. On other plans the same logic has to come from a public app. A quote for a custom Function on a non-Plus store means nobody checked.

Ask for a rule sheet before any code. Each rule goes down in plain words with an example: "carts over $150 with two items from Outerwear get 15% off the cheaper item, and it doesn't combine with the welcome code." You sign it off, and it becomes the test plan.

Ask where the settings live. Functions read their configuration from metafields, so thresholds and percentages can be editable by your team. If moving a threshold from $150 to $175 needs a developer, the build is wrong.

Match the team to the size of the job. In September 2026, nine developers listed Functions work on shopexperts, all with claimed profiles: six freelancers and three agencies, three of them in the UK. A freelancer suits a few rules. A Scripts estate with dozens of rules across several markets is agency-sized.

Red flags. A promise that a Function will look up live prices from your ERP during checkout. Functions don't make external network calls by default, so that design needs the data synced into Shopify first. Also watch for no plan to test combined discounts, and anyone presenting Functions experience as a Shopify Plus Partner credential. It isn't one.

Shopify Scripts to Functions: what to rebuild and what to buy

Script editing and publishing ended on 15 April 2026, and Scripts stopped running on 30 June 2026. A store that missed the switch is now checking out without that logic, usually with no error to show for it. Start from the old Script code if you kept a copy, or from order history: look for discounts, shipping prices and payment options that changed after June.

Line-item Scripts for tiered pricing, bundle discounts, buy-one-get-one variants and member pricing become discount Functions. When the rule changes the line itself, such as merging bundle parts into one line, it becomes a cart transform.

Shipping Scripts that hid, renamed or reordered rates become delivery customisation Functions. Ones that discounted shipping become discount Functions.

Payment Scripts that hid gateways for certain carts, countries or customer tags become payment customisation Functions.

Check the app route before commissioning code. Tiered discounts, hiding a payment method by country and hiding a rate by weight are standard patterns that public Function-based apps exist to handle. A custom Function earns its cost when the rule is specific to your business.

Know what Functions won't do. They run in a sandbox with strict resource limits and no external network calls by default. Logic that depends on outside data, such as ERP pricing or live 3PL stock, needs that data brought into Shopify first, usually as metafields or customer tags. Functions also draw nothing on the page — a rule the buyer needs explained pairs with a checkout UI extension.

How much does Shopify Functions development cost?

A Functions quote depends on how many rules you need and how they interact with the discounts you already run. Typical ranges:

Single Function

$2,000 – $10,000

One discount, delivery or payment rule

Scripts migration

$3,000 – $20,000

Rebuilding Script logic as Functions

Plus specialist rate

$150 – $400

Per hour

Within each tile, configuration and testing drive the spread. A Function with fixed values and one condition sits low. One with a settings screen for your team, stacked conditions and combination rules sits high, because every rule has to be tested against every code and automatic discount already live.

A $100 median starting price is nearer the cost of reviewing your old Script or rule sheet than of a tested Function in production, which the first tile prices. It comes from the nine developers listed here, whose starting prices run from $50 to $4,750 (September 2026). Custom apps with Functions need Plus, so on other plans the answer is a public app, not a quote.

Send the rules you need (or your old Script) to get a quote.

What Functions developers build for Shopify stores

Each Function type does one job in cart or checkout.

Discount Functions

Tiered, bundle, member and volume discounts beyond the native options

Delivery customisations

Hide, rename or reorder shipping options by cart, address or tag

Payment customisations

Hide, rename or reorder payment methods for specific carts

Cart transforms

Merge bundle parts into one line, or expand a bundle into its parts

Cart and checkout validation

Stop checkout when a rule fails, such as a quantity limit

Scripts migration

Rebuilding line-item, shipping and payment Scripts as Functions

Frequently asked questions about Functions development

Can Shopify discount functions combine with my existing discount codes?

Yes, if you set them to. A discount built as a Function works within Shopify's discount classes (product, order and shipping) and their combination settings, just like a native discount. Decide the stacking rules in the rule sheet before the build, not after the first customer complaint. Combinations are where discount builds usually go wrong, so ask for a test matrix that pairs each new discount with every code and automatic discount you run.

Does the Shopify Scripts deprecation affect stores that never used Scripts?

No. Scripts were a Shopify Plus feature, so only Plus stores lost logic when they stopped running on 30 June 2026. If you're on Plus and unsure whether a previous agency set some up, check old invoices and handover notes for Script Editor work, and compare discount and shipping behaviour before and after that date. Non-Plus stores that want Script-like logic get it from public apps built on Functions.

What is a Shopify cart transform used for?

Bundles, mostly. A cart transform can expand one bundle product into its component items, so stock and fulfilment track the parts, or merge separate items into a single bundle line with its own price. Shopify's free Bundles app covers simple fixed bundles, so start there. A custom cart transform earns its place when bundle rules depend on your own data, such as build-your-own boxes with conditional pricing.

Can Shopify payment customization hide payment methods for certain customers?

Yes. A payment customisation Function can hide, rename or reorder payment methods based on cart contents, order total, shipping address or customer tags. Typical uses are hiding cash on delivery above a set order value, removing pay-later options for pre-orders, and showing a bank transfer option only to tagged trade customers. It can't create a new payment method or change a provider's fees.

How do I test a Shopify discount function before customers see it?

Launch it as a discount code only your team knows, then create an automatic discount from the same Function and retire the test code once it behaves. Discount Functions can run either way, so the code version lets you place real test orders on the live store without customers triggering it. Test on mobile, in each currency you sell in, and alongside every discount already running. Ask the developer to watch the Function's run logs for errors through the first week.

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