How Shopify app and API integrations actually work
Every Shopify integration is built on the same handful of building blocks. Understanding them makes it much easier to scope integration work correctly.
Almost every integration is built from the same few pieces
Whatever the integration — accounting software, a custom fulfillment system, a loyalty platform, an internal dashboard — it's almost always built from the same three components: the Admin API to read and write store data, webhooks to react to events as they happen, and, for storefront-facing needs, the Storefront API to expose product and cart data outside Shopify's own theme rendering.
Understanding this makes it much easier to scope integration work honestly. The question isn't "can this be integrated" — almost anything can be — it's which of these building blocks the integration needs, and how much custom logic has to sit between them.
The Admin API: reading and writing store data
The Admin API is how an external system reads or writes orders, products, customers, and inventory. Shopify has moved decisively toward GraphQL as the primary interface — the REST Admin API is now legacy, and new public apps are required to use GraphQL, which also tends to be more efficient since it lets you request exactly the fields you need in one call instead of several.
If you're scoping a new integration today, building it on GraphQL from the start avoids a migration later, even if REST examples are still easier to find in older documentation.
Webhooks: reacting to events in real time
Webhooks solve a different problem: instead of an external system repeatedly asking Shopify "has anything changed," Shopify pushes a notification the moment it does — a new order, an inventory update, a customer editing their details. This is what makes real-time syncing to systems like fulfillment or accounting software practical rather than a constant polling loop.
A properly built webhook integration verifies each request's signature, responds quickly so Shopify doesn't retry unnecessarily, and processes the actual work asynchronously — treating the webhook as a trigger, not the place where slow logic happens.
- Verify the HMAC signature on every incoming webhook before trusting its contents
- Respond to the webhook quickly, then process the underlying work separately
- Handle duplicate or out-of-order deliveries — webhooks aren't guaranteed to arrive exactly once
- Reconcile periodically against the Admin API rather than relying on webhooks as the only source of truth
When to build custom vs. use an existing app
Before scoping custom integration work, check whether an existing app already solves the problem — accounting, fulfillment, and marketing integrations are well-covered categories on the Shopify App Store, and a maintained app is usually cheaper to adopt than to replicate. Custom integration work earns its cost when your workflow, data model, or systems are specific enough that no existing app fits without significant compromise.
Once an integration is live, it becomes part of your store's ongoing footprint — something to account for in regular maintenance, and something worth reviewing periodically the same way you'd review your app stack.
Need a Shopify integration that doesn't already exist as an app?
We build custom Shopify integrations and automations on the Admin API, GraphQL, and webhooks — scoped to what your workflow actually needs.
Common questions
The GraphQL Admin API is Shopify's current path forward and the only option required for new public apps, letting you request exactly the data you need in a single call. The REST Admin API is now considered legacy — existing integrations built on it continue to work, but new integration work should be built on GraphQL.