It’s the fundamental architectural question in Shopify development: “Should this be a theme customization or should it be an app?”
Choosing the right path is one of the most critical decisions you’ll make. Get it right, and you’ll have a feature that is maintainable, scalable, and a pleasure to work with. Get it wrong, and you could be left with a brittle, theme-locked feature that’s a nightmare to update, or an over-engineered app for a simple visual tweak.
Drawing on insights from expert developers, this guide provides a clear decision framework to help you confidently choose the right tool for the job.
The Litmus Test: Presentation vs. Business Logic
The simplest way to start is to ask: “What kind of logic is this?“
1. Choose Theme Customization for Presentation Logic
If the feature is primarily concerned with how things look and where they are displayed, it belongs in the theme. Theme customizations are fast, lightweight, and load instantly with the page.
Good candidates for theme customization:
- Adjusting the styling or layout of a product page.
- Adding a simple, conditional message based on the cart total (e.g., “You’re $10 away from free shipping!”).
- Creating a unique design for an announcement bar or promotional banner.
- Any feature that should be instantaneous and not rely on external API calls.
When theme customization becomes a problem:
- When the logic needs to persist if the merchant changes their theme.
- When you find yourself writing complex, hard-to-maintain JavaScript in your theme files.
- When the feature needs to store data.
2. Choose an App for Business Logic
If the feature involves storing data, running complex calculations, or integrating with third-party services, it belongs in an app. Apps provide the robust backend, database, and API access that themes lack.
Good candidates for an app:
- Storing customer-specific data like wishlist items, loyalty points, or product reviews.
- Implementing custom backend logic, like a complex product configurator or a tiered pricing calculator.
- Integrating with an external ERP, CRM, or marketing platform.
- Any feature that needs to be portable across different themes or even different stores.
When an app becomes a problem:
- When it’s overkill for a simple visual change (e.g., you don’t need an app to change the color of a button).
- When the feature’s reliance on external API calls introduces noticeable latency for the user.
A Decision Framework for Developers
Ask yourself these questions in order. If the answer to a question is “Yes,” it’s a strong signal that you should be building an app.
Question 1: Does this feature need to store data that persists if the theme is changed?
- Yes -> Build an App. This is the clearest dividing line. If data persistence is a requirement, a theme is the wrong tool.
Question 2: Does this feature require complex backend logic or communication with a third-party API?
- Yes -> Build an App. Themes are a frontend concern. Heavy-duty backend logic belongs in an app with a proper server environment.
Question 3: Is this a feature you intend to reuse across multiple client stores or sell on the App Store?
- Yes -> Build an App. An app is a self-contained, portable product. A theme customization is a one-off solution tied to a specific store.
Question 4: Does the feature require access to the Shopify Admin API, GraphQL, or Shopify Functions?
- Yes -> Build an App. These powerful APIs are designed to be accessed from a secure, authenticated backend, which is the domain of an app.
If you answered “No” to all of the above, a theme customization is likely the best, fastest, and most efficient solution.
The Best of Both Worlds: The Hybrid Approach
In many cases, the most elegant solution is a hybrid. This approach uses an app for what it’s good at (data and logic) and the theme for what it’s good at (presentation).
- Example: A product reviews app.
- The App: Stores all the review data, provides an API, and handles the form submission logic.
- The Theme: Uses a Theme App Extension or a simple Liquid snippet to fetch the reviews from the app’s API and render them on the product page.
This hybrid model, often powered by Theme App Extensions, keeps your theme fast and clean while leveraging the power of a dedicated backend. You can even use Metaobjects as a “database-free” way for your app to store structured content directly on Shopify, further simplifying the architecture.
Final Thoughts: Architect for the Future
Choosing between a theme customization and an app is a foundational architectural decision. By using this framework to think through the requirements of your feature—focusing on data, logic, and portability—you can make a choice that will not only solve the immediate problem but also lead to a more maintainable and scalable solution in the long run.
❓ What’s the most complex feature you’ve ever built as a theme customization, and in hindsight, should it have been an app?