Shopify App Development

Some client requirements can't be solved inside a theme. When the logic needs to live outside Liquid — calling Shopify's APIs, reacting to store events, or running its own authenticated interface — that's custom app territory, and it's a different discipline from theme work.

When a Project Needs a Custom App, Not a Theme Section

Themes render storefront pages with Liquid and whatever a theme app extension exposes — that's their job, and it's a good fit for most storefront customization. It stops being enough when a requirement needs server-side logic, has to call an external service on a schedule, needs data that isn't exposed to the theme layer, or requires an authenticated, merchant-facing interface inside the Shopify admin itself. If you're not sure which side of that line a specific request falls on, see theme vs. custom app: what to choose — or send it to us and we'll tell you directly. For work that does fit inside a theme, see Shopify theme development.

Admin API, Storefront API, and Webhooks

The Admin API is how an app manages store data from outside the theme — orders, products, inventory, customers, metafields — and it's where most custom merchant-workflow apps spend their time. We build primarily against the GraphQL Admin API, which is where Shopify has been concentrating new functionality, and use REST endpoints where they're still the more direct fit. The Storefront API is the other side of it: a public-facing API for building custom buying experiences — headless storefronts, custom checkouts-adjacent flows, or interfaces that don't run through a standard theme at all.

Webhooks are what keep an app in sync with the store without polling for changes — subscribing to events like order creation, product updates, inventory changes, or app uninstall, and reacting to them as they happen. Getting webhook handling right (verifying signatures, handling retries, not losing events under load) matters as much as the feature logic itself. For work that connects Shopify to systems outside it entirely — ERP, CRM, shipping — see Shopify API & integration development.

Authentication, Installation, and OAuth

Before any feature work matters, the plumbing has to be correct. Apps install through Shopify's OAuth flow, requesting a specific set of access scopes rather than blanket access to a store. Embedded apps run inside the Shopify admin via App Bridge and authenticate each request with short-lived session tokens instead of long-lived credentials sitting in the browser. Access tokens are scoped per store, and incoming webhooks are verified against Shopify's HMAC signature so the app isn't acting on spoofed requests. This is foundational work — it's also the layer where a rushed build tends to create real security problems later.

Private/Custom Apps vs. Apps for the Shopify App Store

A custom (private) app is built and installed for a single merchant — your client's store — directly, without going through Shopify's App Store review process. It's usually the faster path when the requirement is specific to one client and doesn't need to be distributed anywhere else.

An app intended for the Shopify App Store is a different project: it has to be built for multiple merchants, pass Shopify's app review process, implement the Billing API if it charges for usage, handle mandatory GDPR webhooks, and meet Shopify's broader data-handling and UX requirements. Review timelines and outcomes are set by Shopify, not by us — we build the app to meet the documented requirements, but we don't control or guarantee the review decision. Which path makes sense is worth deciding before development starts, not after, since it changes the architecture.

What We Need to Scope a Custom App

For a technical checklist on scoping API and integration work before it starts, see the Shopify API integration checklist for agencies. Ready to send over the requirements? Submit the project for review. Looking for a standing team for ongoing app and integration work instead of a single build? Apply to the Partner Program.