Custom Shopify Development: Apps, Functions and Features Beyond the Theme
Our custom Shopify development service builds the features your theme settings and off-the-shelf apps cannot: custom apps for your store alone, Shopify Functions that change discount, shipping and payment logic, checkout UI extensions, theme app extensions, product configurators, bundles and customer account features. It is for brands whose products, pricing or customer journey do not fit the standard Shopify setup, and who would rather own a clean solution than stack apps.
Custom work sits within our full Shopify store development service and can be added to a new build or scoped as a standalone project on a live store.
What custom development means on Shopify
Custom Shopify development is building functionality on Shopify's extension points rather than inside the theme alone. It uses custom apps, the Admin GraphQL API, Shopify Functions and UI extensions to add business logic, data models and interface elements that run inside the Shopify Admin, the storefront, the checkout or customer accounts. Done well, it works like a native Shopify feature and keeps working when Shopify updates.
The key word is extension points. Shopify is designed to be extended in specific, supported ways, and custom features built on those routes survive platform changes. Workarounds built on unsupported hacks tend not to.
When settings and apps stop being enough
You probably need custom development if one or more of these sounds familiar:
- Your pricing rules (tiered wholesale, buy-more-save-more by collection, member pricing) need three apps that conflict with each other.
- Customers need to configure a product, choose materials or upload artwork, and the options do not fit Shopify's variant limits.
- You sell bundles or kits and need inventory to come out of the individual components.
- Certain products cannot ship to certain regions, or some payment methods should be hidden for certain orders.
- Your checkout needs an extra field, a delivery date, a gift message or a custom notice.
- Staff repeat the same admin task on every order because Shopify has no button for it.
What we build
Custom apps for your store
A custom app is installed on your store only and talks to Shopify through the Admin GraphQL API with the access scopes it needs and no more. We use custom apps to add admin screens, store custom data, react to webhooks, and host the logic behind Functions and extensions. You own the code and the repository.
Shopify Functions
Shopify Functions let you change how Shopify's back end behaves, running inside Shopify's own infrastructure rather than on a separate server. They are the replacement path for Shopify Scripts and cover the most common custom logic requests.
| Function area | Typical uses |
|---|---|
| Discounts | Tiered pricing, bundle discounts, free gift rules, customer tag pricing, stacking rules |
| Delivery customisation | Hide, rename or reorder shipping methods by product, cart value or destination |
| Payment customisation | Hide or reorder payment methods, for example for high-value or B2B orders |
| Cart and checkout validation | Block orders that break rules such as quantity limits or restricted destinations |
| Cart transform | Expand a bundle into its components or merge items into a bundle line |
Checkout UI extensions
Checkout UI extensions add fields, content and interactive elements to checkout, the thank you page and the order status page, using Shopify's supported components so they stay stable and fast. Examples include delivery date pickers, gift messages, trust notes, upsell offers and loyalty prompts. Some checkout extension points are only available on Shopify Plus, so we confirm what your plan supports before scoping. Deciding what belongs in the checkout for conversion is the job of our checkout optimisation team; we build what they specify.
Theme app extensions
When a custom feature needs a storefront element, we deliver it as a theme app extension: an app block your team can place in any Online Store 2.0 section, or an app embed for site-wide elements. This keeps app code out of your theme files, so it survives theme changes. Storefront layout work that does not need an app belongs with our Liquid theme developers.
Metaobject data models
We design metaobjects for structured content that does not belong on a single product: ingredient libraries, designer or maker profiles, fabric and care guides, store locations, compatibility tables. Products reference them through metafields, so one update changes every product that uses it.
Product configurators and personalisation
For made-to-order, engraved, printed or modular products, we build configurators that capture choices and uploads, show a live price and preview, and pass everything through to the order as line item properties or linked data. Pricing adjustments run through a Function or a bundle structure, not a hidden product workaround.
Bundles and kits
We build fixed and mix-and-match bundles using Shopify's bundle features or a cart transform Function, so the customer sees one bundle while inventory and fulfilment track the individual components.
Customer account and admin features
Using customer account UI extensions, we add features such as reorder buttons, saved configurations, subscription or loyalty information and custom profile fields. Admin UI extensions add actions and blocks inside the Shopify Admin so staff can do repeated tasks from the order or product page.
Build custom or install an app?
We recommend custom code only when it is the better option. A quick comparison:
| Factor | Public app | Custom build |
|---|---|---|
| Time to launch | Fast, often same day | Weeks, depending on scope |
| Fit to your rules | Close, with compromises | Exact |
| Ongoing cost | Recurring subscription | Hosting where needed and maintenance |
| Page weight | Varies, sometimes heavy | Only what the feature needs |
| Ownership | Vendor controls roadmap | You own the code |
If a well-maintained app covers the need, we will recommend it.
Where custom development ends and other services begin
- Connecting Shopify to an ERP, PIM, 3PL, CRM or accounting system is an integration project handled by our ERP, 3PL and systems integration team.
- Recurring scripted jobs, such as nightly price updates, bulk product edits or scheduled reports, belong to our API automation service.
- Plus-only work such as migrating Shopify Scripts, B2B catalogues and expansion stores is covered by our Shopify Plus development work. Many projects use both services together.
Engineering standards
- Supported APIs only. Functions, UI extensions and the Admin GraphQL API, pinned to a stable API version and updated as Shopify releases new versions.
- Least-privilege access. Each app requests only the scopes it uses.
- Verified webhooks. Incoming webhooks are signature-checked, idempotent and logged.
- Tested logic. Functions and pricing rules are tested against real cart scenarios, including edge cases.
- Your code, your repository. Code lives in a Git repository you own, with a README and deployment notes.
- Staged releases. Everything is tested on a development store or unpublished theme before it touches live orders.
Problems we solve
| Problem | Cause | What we build | What it moves |
|---|---|---|---|
| Discount apps conflict at checkout | Several apps applying overlapping rules | One discount Function with clear stacking logic | AOV, margin, support tickets |
| Configurable products create messy orders | Options captured in notes or hidden products | Configurator with structured line item data | Order accuracy, fulfilment time |
| Bundles break stock counts | Bundles set up as separate products | Cart transform or native bundles tied to components | Stock accuracy, oversells |
| Wrong shipping methods shown | Rate rules cannot see product restrictions | Delivery customisation Function | Checkout completion, fulfilment errors |
| Staff repeat manual steps on every order | No admin action for the task | Admin UI extension or custom app action | Staff hours per order |
How a custom build runs
1. Audit and baseline
We map the current workaround: which apps are involved, what staff do by hand, where orders or discounts go wrong, and what it costs in time. You receive a written summary with the recommended approach, including whether an existing app would do the job.
2. Strategy and scope
We write a functional specification covering rules, edge cases, extension points, data model and plan requirements. The fixed scope and fee are agreed before development starts.
3. Build and fix
Development runs on a development store or an unpublished theme with test orders. You test the feature yourself on preview links and sign off each part before it is deployed.
4. Launch and track
We deploy at a low-traffic time, watch logs, orders and error reports closely, and hand over documentation. Maintenance and future changes can be scoped as follow-on projects.
Tools and technology
Shopify CLI, the Admin GraphQL API, Shopify Functions, checkout UI extensions, customer account and admin UI extensions, theme app extensions, metafields and metaobjects, webhooks, Polaris components for admin interfaces, GitHub and development stores for testing.
Outcomes the work can influence
- Average order value and margin, through correct discount and bundle logic.
- Checkout completion, when shipping and payment options match the order.
- Order accuracy and fulfilment speed for configurable products.
- Staff hours spent on manual workarounds.
- Number of apps and monthly app costs.
Who this service suits
- Brands with pricing, bundling or product rules the standard admin cannot express.
- Stores selling made-to-order or personalised products.
- Teams replacing several overlapping apps with one owned feature.
- Shopify Plus merchants moving custom logic from Scripts to Functions.
How pricing works
Custom work is quoted as a fixed project fee after a discovery call and a written specification. Cost depends on the number of extension points, the complexity of the rules, the data model, and whether the feature needs a hosted app. Request a custom development quote.
Frequently asked questions
A custom app is built for and installed on your store only, and you own the code. A public app is sold to many stores through the Shopify App Store, and the vendor controls its features, pricing and roadmap.
It depends on how they are delivered. Functions distributed in public apps work across plans, while some Function and checkout customisation options for custom apps require Shopify Plus. We confirm what your plan supports during discovery before recommending a route.
Yes. We audit each Script, rebuild the logic as discount, delivery or payment Functions, test them side by side, and switch over once the results match.
It is a fixed fee based on your specification. A single Function or theme app extension is a small project, while a configurator with a custom app, admin screens and checkout extension is a larger one. We quote in writing after scoping.
Functions and UI extensions run on Shopify's infrastructure. If a feature needs a custom app back end, we set up hosting in an account you own. The code sits in your repository, so any developer can maintain it.
Features built on supported extension points are designed to keep working through platform updates. We pin each app to a stable API version and plan updates as Shopify retires older versions.
Related services
- Shopify Plus builds, B2B and Scripts migrationPlus-specific features that often pair with Functions.
- Custom sections and Online Store 2.0 templatesstorefront work that sits alongside app blocks.
- Connecting Shopify to back-office systemsERP, 3PL and CRM data sync.
- Scheduled jobs and bulk updates through the APIrecurring automated processes rather than new features.
- Improving checkout completiondeciding what the checkout extensions should do.
Talk to a Shopify developer about your feature
Describe the feature, the rules behind it and what you use today. We will tell you whether an app, a Function or a custom build is the right route, and send a written scope and fixed fee. Talk to a developer about your custom feature.