Shopify App Build Journey
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📜 Shopify 101 — For the Developer Who Knows Nothing About It

The person reading this file: knows how to write code, understands a bit of marketing, has zero knowledge of Shopify. Goal: after 30 minutes of reading, be able to answer "what is a Shopify app, what am I going to build, where does the money come from". No setup, just a clear picture in your head.

1. What exactly is Shopify?

An e-commerce SaaS. A business pays a monthly fee and gets a ready-made online store in return: product management, cart, payments, shipping, tax, admin panel. You open a store without writing code.

There are three parties in the ecosystem:

Party Who What they want
Merchant (seller) The store owner. Our customer. More sales, less manual work
Shopify The platform Ecosystem growth, commission
Partner / Developer Us Sell tools to merchants and make money

Critical point: our customer is the merchant, not Shopify. Shopify is just the distribution channel — the intermediary that runs the App Store, issues the invoice and collects the money.

2. What is a Shopify app?

Software that does a job Shopify doesn't do on its own, which the merchant installs into their store.

Examples (real App Store categories):

  • Automatically collecting and displaying product reviews
  • WhatsApp/SMS reminders for abandoned carts
  • Automatic reorders to the supplier when stock runs low
  • Printing shipping labels, managing returns
  • "Buy this too" recommendations on the product page

Technically, the app does not run on Shopify's servers. It is a normal web application sitting on your own server (in our case, on Coolify). Shopify only:

  1. Sends the merchant to you via OAuth,
  2. Shows your application inside the admin panel in an iframe,
  3. Gives you an access token to access the store's data.

So it's a web app as you know it. What's new: the authentication flow, the APIs and billing are tied to Shopify.

3. Mental model — the pieces

                 ┌────────────────────────────────────────────┐
                 │  Shopify Admin (what the merchant sees)    │
                 │  ┌──────────────────────────────────────┐  │
   merchant ───► │  │  <iframe> YOUR APP                   │  │
                 │  │  (running on your server)            │  │
                 │  └──────────────────────────────────────┘  │
                 └────────────────────────────────────────────┘
                            │  Admin GraphQL API (you → Shopify: read/write data)
                            ▼
                 ┌────────────────────────────────────────────┐
                 │  Shopify: products, orders, customers      │
                 └────────────────────────────────────────────┘
                            │  Webhook (Shopify → you: "an order came in")
                            ▼
                     your server / your database

There are three directions, don't mix them up:

  • iframe → the merchant sees your UI inside the admin (this is called an embedded app).
  • API call → you ask Shopify for data. GraphQL. (The REST API is legacy now; don't write new code against it.)
  • Webhook → Shopify notifies you of an event. Order created, product deleted, app uninstalled.

4. Glossary — you can't move forward without these

Term What it means
Merchant The store owner. Your customer.
Store / shop A single store. Has a permanent name like something.myshopify.com.
Partner account Your developer account. Free. Your apps and test stores live here.
Development store A free test store filled with fake data. Can't make real sales. This is where you develop.
Embedded app An app that opens in an iframe inside the admin. This is the standard.
App Bridge Shopify's library that lets your JS inside the iframe talk to the admin outside it (open a modal, redirect, show a toast).
Session token Identity in an embedded app. Because it's an iframe, cookies can't be trusted; a short-lived JWT comes with every request.
Access token The key you receive when a merchant installs the app, granting access to that store's API. One per store.
Scopes Permissions. Like read_products, write_orders. Every permission you ask for is shown to the merchant on the install screen — asking for too many lowers installs.
Admin GraphQL API The main API for reading/writing store data.
Webhook An event notification Shopify sends you (HTTP POST).
Extension The part of your app that injects code somewhere outside the admin (see below).
Theme The store's storefront — a theme written with Liquid templates. A separate world from the app.
Liquid Shopify's theme templating language. You'll see little of it writing apps, a lot of it if you get into theme work.
App Store apps.shopify.com — the marketplace where apps are listed. Getting in requires review.
Custom app An app written for a single store, not listed on the App Store. No review.
Shopify Functions WASM code that runs on Shopify's own infrastructure (discount logic, shipping rules). Rare but powerful.

5. Types of apps — deciding what to build

Public app — Listed on the App Store, anyone can install it. Scales, but goes through the review process. 👉 This is our target.

Custom app — For a single merchant. No review, fast. Like consulting work; doesn't scale, but brings in the first money quickly and teaches you the real problem.

Extensions — Parts of your app that reach outside the admin:

  • Theme app extension → adds a block to the storefront (e.g. a review box on the product page)
  • Checkout UI extension → adds fields to the checkout page (some parts require the Plus plan)
  • Admin UI extension → adds buttons/panels to the admin's own pages
  • Shopify Functions → runs discount/shipping logic inside Shopify

At the start, an embedded admin app alone is enough. Extensions come later.

6. How is money made?

You charge the merchant a subscription (typical: $9–99/mo, some usage-based). You don't collect the money yourself: via the Billing API, Shopify adds it to the merchant's existing invoice, charges it, and pays you. No credit card integration — this is a huge convenience.

Shopify takes a revenue share. The current general framework: 0% up to a certain annual threshold, a share above it. The rates change — confirm them in the Partner docs at the time you apply, don't trust the number here.

A realistic sense of scale: $30/mo × 50 merchants = $1,500/mo. That's a small-to-mid but real app on the App Store. Set your target from here, not from "there are millions of merchants".

7. Why this business is attractive for a developer — and where the trap is

Attractive:

  • Payment infrastructure, authentication and the distribution channel come ready-made.
  • Your customer is already a paying business; no B2C "user waiting for free stuff" problem.
  • Merchants are easy to find: they openly talk about what they sell, their revenue, their problems.

Trap:

  • App Store competition is fierce; every popular category has 50+ apps.
  • Merchants install apps like items in a shopping cart and delete them a month later. Churn is high.
  • A "nice app" doesn't sell; a measurable result sells (conversion went up, saved this many hours).
  • The biggest mistake: learn the platform, write code for 3 months, then publish something nobody wants.

That's why in the roadmap the technical warm-up is deliberately short, followed by merchant conversations.

8. The 5 sentences that need to be clear in your head

  1. Shopify app = a normal web application running on my own server, shown in the admin via an iframe.
  2. Merchant installs → OAuth → I get an access token for that store.
  3. I read data with the Admin GraphQL API, I hear about events via webhooks.
  4. Shopify collects the money via the Billing API and pays me.
  5. The hard part isn't the code; it's which merchant's which pain I'm solving.

9. What's next

We got this far without installing anything. Setup and the first running application: 👉 LEARNING.md — Session 1.

Sources: shopify.dev (official docs), partners.shopify.com. This file gets corrected as we learn — if you see something wrong, change it and add a date.