Shopify has multiple APIs, and for many developers, that’s where the confusion starts.
Which API should you use for themes? Which ones are for apps? And why does Shopify keep pushing GraphQL?
In this article, we’ll break down Shopify APIs in plain English. I’ll explain what each API is for, how they fit together, and which ones you actually need depending on what you’re building.
What Is the Shopify API?
At a basic level, an API is a bridge that lets different systems talk to each other.
In Shopify, the APIs allow you to:
- Read data like products, collections, and carts
- Write data such as updating carts or modifying products
- React to events like orders being created or updated
Instead of manually clicking around in the admin, the APIs let you interact with Shopify programmatically.
This is what powers themes, apps, headless storefronts, and integrations.
How Shopify Separates Frontend and Backend APIs
One of the most important concepts I had to understand early on is how Shopify separates APIs based on where they run and what data they expose.
Storefront vs Admin
- Storefront APIs are used to power the customer-facing experience
- Admin APIs are used to manage store data behind the scenes
Public vs Private Data
- Frontend APIs expose customer-safe data
- Backend APIs access sensitive data like orders and customers
This separation is what keeps Shopify stores secure while still allowing deep customization.
Shopify AJAX APIs (Theme Development)
The theme Ajax API lets you add items to the cart or update a specific section on your website without reloading the entire page.
What It's used for
- Adding items to the cart
- Updating cart quantities
- Fetching product recommendations
- Powering predictive search
- Refreshing individual sections (Section rendering API)
The AJAX API only exposes storefront-safe data, which is why it can be used directly in the browser.
It's limited strictly to storefront use cases.
Shopify Admin API
The Admin API is the core API you use when building Shopify apps.
This API gives access to sensitive store data, such as:
- Orders
- Customers
- Products
- Inventory
Because of this, it must be used server-side, never directly in the browser.
Requests are authenticated via API Keys / Tokens and sensitive data never reaches the storefront.
First Steps:
Shopify provides GraphiQL, an interactive tool that lets you explore the Admin API inside a store.
You can configure the exact same access scopes that your app would have and practice writing your first GraphQL queries.
If you've never worked with GraphQL, here is a quick guide on how to get started:
REST vs GraphQL in Shopify
Shopify has been steadily moving toward GraphQL-first APIs, especially for the Admin API.
GraphQL gives you way more control than REST.
Instead of pulling a potentially large response with all sorts of data, GraphQL lets you specify exactly the data you want.
By avoiding this overfetching it improves performance at scale, and makes working with complex, connected data much cleaner.
Shopify Webhooks (Reacting to Events)
Webhooks let Shopify notify your app when something happens.
Polling Shopify in a loop to check for changes is wasteful and slow — for example, repeatedly asking the API every 10 seconds whether a new order exists, even when nothing has changed.
Webhooks flip this around: They let you subscribe to certain topics, and Shopify notifies your server the moment something happens (like an order being created).
Shopify Storefront API (Headless & Custom Frontends)
The Storefront API is used when you’re building custom storefronts outside of Shopify themes.
Common Use Cases
- Headless websites
- Mobile apps
- Kiosks or embedded shopping experiences
What It Can Access
- Products and collections
- Carts and checkout
- Customer-safe data only
The storefront API also doesn't have rate limits, so that your custom storefront also work during flash sales and traffic spike.
Shopify Functions
Shopify Functions often confuse developers because they’re not traditional APIs.
What Functions Are
- Small pieces of logic that run inside Shopify
- Used to customize pricing, discounts, and cart behavior
Which Shopify API Should You Use?
Here’s a simple breakdown:
- Themes → Shopify AJAX API
- Apps Data → Admin API (GraphQL)
- Headless storefronts → Storefront API
- Event handling → Webhooks
- Logic overrides → Shopify Functions
Next steps for Shopify developers:
If you’re new to Shopify’s APIs, don’t jump straight into random endpoints, first understand how the pieces fit together.
- Theme development: start with the theme APIs and Liquid. They’re easier to use and cover most storefront needs.
- App development: learn Shopify’s GraphQL properly, practice queries in GraphiQL, and understand how the Admin API works.
For a beginner-friendly walkthrough that ties all of this together, watch the videos below.