Shopify Service

Shopify App
Development
built for your exact needs.

Sometimes the App Store just doesn't cut it. Maybe the integration you need doesn't exist, or the closest app does 80% of what you want but not the 20% that actually matters. We've been building private apps, public App Store apps, Shopify Functions, admin UI extensions, and custom API integrations since 2017. Our team is fully in-house, based in New York, and we don't hand your project off to freelancers. Every app goes out on Shopify's current Admin API and Storefront API.

2017
Shopify Partner since
30+
In-house developers
5.0
Partner rating
APIv1
Latest Shopify APIs used

Private app or public app: we build both

Which type you need comes down to who you're building for. A private app is yours alone. It won't appear in the App Store, can't be installed by anyone else, and it's the right call when you've got a workflow or integration that no existing app handles properly. A public app is a product in its own right, listed on the App Store where any merchant can find and install it. We've built both kinds. Once we understand what you're trying to do, we'll tell you which direction makes sense. If you're pairing a new app with a full store build, that's worth discussing in the same conversation.

Option A

Custom Private App

Built for your store only. It isn't listed anywhere, it's installed via a direct link, and other merchants can't see it. This is what you need when nothing in the App Store fits your situation: whether that's because your ERP has a proprietary API, your pricing logic is too specific for generic discount apps, or your internal workflow needs something built around how your team actually operates.

Common use cases
NetSuite, SAP, or WMS integration
Custom order routing and fulfilment logic
Product configurator or custom bundle builder
B2B pricing rules and account-level discounts
Internal admin dashboards for ops teams
Loyalty programme logic and subscription rules
Admin APIShopify FunctionsWebhooksApp Bridge
Option B

Public App Store App

Built to Shopify's App Store specs: OAuth 2.0 authentication, multi-merchant support, and Shopify's billing API wired in from day one. This is the route if you're a founder building a product for other merchants, or an agency that wants branded tooling across a client portfolio. It's a bigger build, and Shopify's review process adds time. But once it's listed, any merchant can install it. We've taken apps through that process before and we know what Shopify's reviewers look for.

Suitable for
SaaS founders building Shopify-native tools
Agencies offering branded merchant solutions
Niche functionality missing from the App Store
Branded apps for enterprise clients
Internal tools scaled across a merchant portfolio
Revenue-generating App Store products
OAuth 2.0Billing APIAdmin APIApp Store Review

Custom commerce logic: running inside Shopify

Shopify Functions let you write custom server-side logic that runs inside Shopify's own infrastructure. Not on your servers, not through a third-party webhook chain. They replaced Shopify Scripts and now cover discount logic, shipping rates, payment methods, and cart transformations across all plan tiers, not just Plus. If you've been hitting the ceiling of what standard discount settings or shipping rules can do, Functions are usually the answer. They're also how you build the kind of Shopify Plus checkout experiences that actually set a brand apart from its competitors.

For B2B merchants especially, Functions open up things that weren't really possible before. Customer-tag-based pricing tiers, account-level discount schedules, shipping rate logic tied to product category and destination at the same time. We scope and build Functions either as standalone projects or as part of a larger custom app engagement, depending on what makes sense for your store. If you're also thinking about performance improvements, replacing multiple third-party app scripts with a single custom app often helps there too.

Discount Functions
Custom Discount Logic
Percentage and fixed-amount discounts, buy-X-get-Y, tiered volume pricing based on quantity or customer tag, B2B-specific discount schedules, and account-level pricing rules. Anything the standard Shopify discount manager can't handle, a custom Discount Function can.
Shipping Functions
Custom Shipping Rate Logic
Dynamic rates calculated from product type, customer tags, cart weight, destination, dimensional weight, or combinations of those — all at checkout time. You can also show, hide, or relabel carrier options depending on what's actually in the cart.
Payment Functions
Payment Method Customisation
Show or hide payment methods based on cart total, customer location, product type, or customer-tag conditions. Useful for things like hiding bank transfer at checkout for guest customers, or surfacing trade account payment terms for B2B buyers only.
Cart & Checkout Functions
Cart Transform & Validation
Custom line item transformations, quantity enforcement, product bundling at the cart level, and checkout validation rules. If your business has cart logic that doesn't fit into Shopify's standard settings, a Cart Transform or Validation Function handles it at the platform level, not through workaround scripts.

Connect Shopify to any system

The App Store has connector apps for the popular platforms. But if you're running NetSuite, SAP, Microsoft Dynamics, or a custom-built backend with its own API, you've probably found the off-the-shelf connectors don't quite do what you need. We build the integration layer from scratch, using Shopify's Admin API and Webhooks on the Shopify side and whatever the target system exposes on the other. Clients working with us from Los Angeles and beyond run the full range of systems, and we've seen most of them. Bidirectional sync matters. Most integrations aren't one-way. Orders need to push into your ERP. Inventory changes in your WMS need to come back into Shopify. We design for that from the start, with error handling, retry logic, dead-letter queuing, and logging built in, not added as an afterthought. If you're also in the middle of a platform migration, getting the integration architecture right before you go live is worth the extra planning time.

01
ERP & Business System Integrations
SAP, Oracle NetSuite, Microsoft Dynamics, Sage. We've built two-way sync of orders, products, customers, and inventory between Shopify and core business systems. We map your data schema, handle the transformation logic, and build in proper error recovery so a failed sync doesn't silently drop data.
02
Warehouse & Fulfilment (WMS / 3PL)
Custom integrations with WMS platforms and 3PL providers. Orders push to the warehouse on the right trigger, tracking numbers come back automatically, and inventory levels stay in sync. It's built on Shopify Webhooks and the Admin API's fulfilment endpoints.
03
CRM & Marketing Platform Integrations
Deeper integrations with Salesforce, HubSpot, or bespoke CRM systems than the standard connector apps can manage. Customer lifecycle events, purchase history, loyalty programme data, and segmentation signals — synced with the field mapping your team actually needs.
04
Custom Backend & Proprietary APIs
If your business runs on a custom-built backend with its own API, we build the Shopify integration layer that connects it reliably. That includes data mapping, transformation logic, and error handling that holds up under real production load.
05
Webhook-Based Event Automation
Event-driven integrations using Shopify Webhooks that trigger actions in external systems the moment something happens: order placed, payment captured, refund issued, inventory threshold reached. Real time, not batch.

Why the App Store is not always enough

The Shopify App Store has over 8,000 apps. But generic apps are built to serve the broadest possible audience, not your specific business logic, your proprietary systems, or your exact operational requirements. Here's when a custom app is the right call.

01
No available app covers your exact use case
When your business needs logic that no existing Shopify app supports, a specific integration, a unique pricing model, or a custom product configuration tool, a custom app is the only real path forward. We build exactly what you need, without feature bloat or half-measures.
02
Existing apps are slowing your store down
A lot of common app use cases can be rolled into one custom private app, cutting out the JavaScript overhead of five separate third-party scripts loading on every page. It's one of the ways a custom app can improve store performance while giving you exactly the functionality you need.
03
You need a connection no standard app provides
If your business uses a proprietary ERP, a legacy WMS, or any system that doesn't have a Shopify connector, a custom integration app is the only way to connect it. We build the middleware layer, data mapping, and sync logic from scratch.
04
Shopify Plus checkout requires custom logic
Shopify Plus unlocks Checkout Extensibility and Shopify Functions for custom checkout experiences. If you need tiered B2B pricing, custom shipping rules, or specific payment method control, Shopify Functions built into a custom app is the right technical approach.
05
You want to own your functionality entirely
Third-party apps can be deprecated, change pricing, or alter features at any time. A custom private app you own gives you full control. There's no dependency on a vendor's roadmap, no surprise cost increases, and no risk of a critical app vanishing from the App Store.
06
Built by in-house Shopify specialists
Every app we build is developed by our permanent in-house team. We don't use freelancers or subcontractors. We've been working with Shopify's APIs since 2017 and we've got direct experience with every significant API change the platform has made in that time. Check our portfolio to see some of what we've shipped.

Built on Shopify's current API stack

Every app we build uses Shopify's current-generation APIs and frameworks, not deprecated patterns. That matters for long-term compatibility, easier maintenance, and full access to what the platform can actually do today.

Core API
Shopify Admin API
GraphQL & REST: products, orders, customers
Commerce Logic
Shopify Functions
Discounts, shipping, payments, cart transform
Storefront
Storefront API
Custom buying experiences & headless commerce
UI Framework
App Bridge & Polaris
Native-feeling admin UI components
Events
Webhooks
Real-time event-driven data pipelines
Auth
OAuth 2.0
Secure multi-merchant authentication for public apps

How we build a custom Shopify app

From discovery to deployment, every custom app project follows a structured process with clear milestones, regular check-ins, and full documentation at handover. You're not left guessing where things stand.

Phase 01
Requirements Discovery

We map your complete requirements in detail before a line of code is written. Every feature, data flow, API integration point, user role, and edge case gets documented. The result is a technical specification that forms the agreed scope of work, timeline, and cost. No surprises later.

Phase 02
Architecture & API Design

We design the app architecture: picking the right Shopify APIs, defining the data model, planning the integration layer, and working out the admin UI structure if one's needed. For complex integrations, we produce data flow diagrams for your review before development starts.

Phase 03
Development & Integration

Core development happens in a staging environment connected to your Shopify development store. We build in milestones with working demos at each stage. Integration endpoints are tested against your actual systems, not mocked data, before each milestone sign-off.

Phase 04
QA, Testing & Deployment

We test every user flow, edge case, error state, and API failure scenario before anything goes near production. For live deployments, we coordinate the rollout, verify everything against the live store, and watch it closely for the first 48 hours after launch.

Phase 05
Documentation & Handover

We hand over full technical documentation covering the app architecture, API endpoints used, configuration options, admin user guide, and maintenance notes. Your team knows how to operate and manage the app, and we're still available for ongoing support and future development if you need it.

Shopify app development questions answered

The questions we get most often about custom Shopify app development, answered with the kind of detail that comes from building on the platform every day since 2017.

Ask us directly
What is a custom Shopify app?

A custom Shopify app is software built specifically for a Shopify store: either as a private app (used only by one store, not available on the App Store) or a public app (listed on the Shopify App Store for any merchant to install).

You’d build a custom app when the App Store doesn’t have what you need. That might be a proprietary ERP integration, unique discount logic, a bespoke product configurator, or a custom admin interface for complex store operations. They’re built using Shopify’s official APIs: Admin API, Storefront API, Webhooks, and Shopify Functions.

What is the difference between a private and public Shopify app?

A private Shopify app is built for a single store. It isn’t listed on the App Store, can’t be installed by other merchants, and it’s the right choice for custom business logic, proprietary integrations, and internal workflows unique to your operation. You install it on your store via a direct installation link.

A public Shopify app goes through Shopify’s review and approval process and gets listed on the App Store where any merchant can discover and install it. Public apps require OAuth-based authentication for multiple merchant installations, a billing integration using Shopify’s subscription API, and compliance with Shopify’s submission guidelines. It’s essentially building a software product — significantly more involved than a private app.

How much does it cost to build a custom Shopify app?

Cost depends on app complexity, features, APIs used, and backend infrastructure requirements:

Simple private app: automating a workflow or providing a basic integration: $1,500 to $5,000.

Complex private app: custom admin UI, multiple API integrations, webhook automation, and custom business logic: $5,000 to $20,000.

Full public App Store app: OAuth, multi-merchant support, billing, polished onboarding, and App Store review process: $15,000 to $50,000+.

We provide a detailed, itemised estimate after a discovery session where we fully document your requirements. No guessing on either side.

How long does it take to build a Shopify app?

Timeline depends on scope:

Simple private app: 2 to 6 weeks.

Complex private app: 6 to 12 weeks.

Full public App Store app: 3 to 6 months from kick-off to App Store listing, including the Shopify review process which typically takes 2 to 4 weeks.

Every project starts with a milestone-based plan. You’ll know the exact timeline and what’s being delivered at each stage before we write a line of code.

What are Shopify Functions and when do I need them?

Shopify Functions let custom server-side logic run directly within Shopify’s infrastructure, extending discount, shipping, payment, and cart behaviour beyond what standard Shopify settings allow. They’re the current-generation replacement for Shopify Scripts, and they work across all Shopify plans, not just Plus.

You need Shopify Functions when you require: custom discount logic (tiered pricing, B2B-specific discounts, complex buy-X-get-Y rules), custom shipping rates based on product type, customer tags, or cart conditions, payment method filtering to show or hide specific options based on cart state, or cart validation to enforce custom quantity or product rules at checkout.

Can you integrate Shopify with my ERP or custom backend?

Yes. We’ve built integrations between Shopify and a wide range of third-party systems, including ERP platforms (SAP, Oracle NetSuite, Microsoft Dynamics), warehouse management systems, fulfilment providers, CRMs (Salesforce, HubSpot), inventory tools, accounting software, and custom proprietary backends.

Integrations are built using Shopify’s Admin API and Webhooks, with a custom middleware layer that handles data transformation, field mapping, error handling, and retry logic. Most integration projects require bidirectional sync, so we design for reliability and observability from the start, not as an afterthought.

What is a Shopify Admin UI Extension?

detail page, Product page, or Customer profile page. Your team can view data from external systems, trigger actions, or manage custom fields without leaving the Shopify admin.

Admin UI extensions are built using Shopify’s App Bridge framework and React. They’re a key part of private apps where you need to give store staff a custom operational interface. That could be displaying fulfilment status from your WMS, showing loyalty account details from your CRM, or triggering custom workflows directly from the order view.

Do you build apps using the latest Shopify APIs?

Yes. All apps we build use Shopify’s current-generation APIs: Admin API (GraphQL), Storefront API, Shopify Functions, App Bridge for admin UI, and Webhooks for event-driven data pipelines. We don’t build on deprecated API patterns or legacy approaches.

Shopify releases new API versions quarterly. We monitor version changes and flag any breaking changes that affect apps we’ve built. Our maintenance service covers keeping apps current with API version updates so you don’t get caught out by deprecated endpoints.

Will you maintain the app after it is built?

Yes. We offer ongoing maintenance and support for all apps we build. That covers API version updates, bug resolution, performance monitoring, and feature additions as your requirements grow.

We’ve got retainer plans for clients who need regular development, priority support response, and proactive monitoring. For any business-critical app, we’d strongly recommend a maintenance agreement. Shopify’s API deprecation cycles mean apps need regular attention to stay fully functional over time.

What our clients say about working with us

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★★★★★

"Axis Web Art developed our website. They are easy to work with, thorough, and responsive. We have been very happy with their service."

GL
Garrett Leather
Roberta Sand, Marketing Director
★★★★★

"Great work, they know how to change your theme effectively without any issues. Fixed a few tiny issues moments after identifying them. Always a pleasure to work with this team of highly skilled players."

TC
Timothy
Founder, Timothy De Clue Collection
★★★★★

"We crafted a soothing online shopping experience for Bubbaroo, a leading Australian baby sleep bag brand. Our Shopify store design and development focused on safety, comfort, and parent peace of mind."

BU
Bubbaroo
Nicole Cassey, Founder
Start your project

Got a Shopify problem the App Store hasn't solved?

Tell us what you need to build: the functionality, the systems it needs to connect to, and the problem it needs to fix. We'll look at the requirements and put together a clear technical proposal. We've been doing this since 2011 and we're a Shopify Partner since 2017, so we know the platform well enough to tell you what's actually possible.

No-obligation conversation · Response within 24 hours · Official Shopify Partner since 2017