Custom Shopify App vs Public App: When to Build Your Own

The old term 'private app' still shows up in searches. Today, Shopify's custom apps help page describes a custom app as one that you or a developer builds exclusively for your store. New custom apps are created and managed in Shopify's Dev Dashboard. Legacy custom apps created in the Shopify admin before January 1, 2026 can still be managed from the admin.

Shopify's app distribution documentation adds two details that matter for planning. Custom distribution covers a single store or multiple stores in the same Plus organization, and you can't change an app's distribution method after you choose it. Custom apps also can't charge merchants through Shopify's app billing system, which doesn't matter when the merchant is the one paying for the build.

Custom apps make sense when the job is specific to how your business runs, not a common storefront feature. A reviews widget is a solved problem. Syncing stock between Shopify and the warehouse system your company picked ten years ago usually isn't.

A quick test: if you can describe the job as 'when this happens in Shopify, do that in another system,' it's an integration, and integrations are where custom apps tend to pay back. If the description starts with 'on the product page,' look for a public app or a custom theme section first, because storefront features are cheaper to build in the theme.

For most storefront features, a well-supported public app is cheaper and safer than custom code. The vendor spreads development, security and API upgrade costs across many merchants, and you get improvements you didn't pay to build.

Public apps have a cost that doesn't show on the invoice, though. Each one can add scripts to your pages, and some leave code behind after you uninstall them. If your store has cycled through several apps, see how to remove leftover Shopify app code, and check what each app adds to interaction delay using our guide to Shopify INP and Core Web Vitals.

Shopify has moved a lot of custom logic into supported extension points. According to Shopify's Functions documentation, Functions customize backend logic such as discounts, payment and delivery options, cart and checkout validation, order routing and bundles. There's an important plan limit: only stores on a Shopify Plus plan can use custom apps that contain Function APIs, although public apps with Functions work on all plans.

Shopify Flow is a free app on the Basic, Grow, Advanced and Plus plans. It watches for store events and runs actions when conditions are met, such as tagging high-risk orders or alerting staff when stock runs low. Stores on Grow, Advanced and Plus can use its Send HTTP Request action, which can call another system's API, and that covers some integrations people assume need a custom app.

Checkout is the third place to look. Checkout UI extensions let apps add content and fields to checkout, but Shopify limits extensions on the information, shipping and payment steps to Plus stores. If your idea depends on changing those steps and you're not on Plus, rethink the idea before you scope the app.

The build quote is the smallest part of the decision. A custom app has running costs, and the most predictable one is Shopify's release schedule. Shopify's API versioning documentation says a new API version ships every three months, each stable version is supported for at least 12 months, and consecutive versions overlap by at least nine months. If an app calls a version that's no longer available, Shopify falls forward to the oldest supported version, which can change behavior without warning. Budget for a review at least once a year and small changes more often.

New integrations should use the GraphQL Admin API. Shopify's REST Admin API has been a legacy API since October 1, 2024, so a developer proposing REST for new work is adding maintenance debt on day one.

Use the worksheet below and fill in your own numbers. As an illustrative example only: three overlapping apps at $50, $100 and $150 a month add up to $300 a month, or $10,800 over three years. A custom app replacing them has to come in below that once you add its build cost, hosting and three years of maintenance, or deliver something the apps can't, such as removing hours of manual work each week.

The best custom apps usually replace manual work that happens every day. They tend to run in the background, not on your storefront.

Integration apps fail in quiet ways: an order that never reached the ERP, a stock level that stopped updating on a Sunday. The build plan should spend as much time on what happens when something goes wrong as on the happy path.

A sensible project runs in stages, with a working version on a development store before anything touches live orders. Ask any developer you're considering how they handle each stage below, and what you'll be able to see and test at the end of it.

Whoever controls the app's developer account, code repository and hosting controls the app. Put all three under your company's accounts from day one, and give your developer access rather than the other way around.

Ask for the smallest set of access scopes the app needs. An order export doesn't need write access to products. In your Shopify admin, only people with the App development permission can create or manage custom apps, so check who has it.

A clear brief keeps estimates comparable and stops scope creep. Send the same one to every developer you talk to, and ask each for a line-item estimate plus their view on whether Flow, Functions or an existing app could replace part of the build. For how different providers price this work, see Shopify developer rates.

Pixel2Tech builds store-specific integrations and internal tools through our custom platforms and apps service. The checklist below works with any developer.