Custom Shopify app development — process, pricing and timeline

Why a custom Shopify app?

The Shopify App Store holds thousands of ready-made apps, but sometimes none fits your exact workflow. Perhaps you want to display data from an internal system live in your shop, or you have a unique order process that off-the-shelf apps can't handle. Then a custom Shopify app is the only solution that truly works.

I built two public apps myself — Repair Manager (repair management for jewellers) and Sendcloud Connector (shipping integration) — and regularly create private custom apps for clients who need a specific integration or workflow. What I've learnt: a good app doesn't start with code, but with a clear scope.

Scope first, then build

A custom Shopify app always solves a specific problem. Describe it concretely: "I want customers to upload their own engraving example and have that image sent automatically to our laser machine" is useful. "I want something with personalisation" is too vague.

Good developers ask questions until the scope is clear and propose what is and isn't included in version one. That prevents you paying for functionality you'll never use, or discovering halfway through that a crucial integration is missing. Always ask for a written proposal with a fixed price and a concrete timeline.

Private custom app or public app?

If the app is only for your shop, you build a private custom app. You install it directly without a review process, and you don't need to worry about billing or support for other shops. That saves time and cost.

If you want to sell the app later or offer it to other Shopify merchants, you must go through Shopify's app review and meet stricter requirements around GDPR, security and user interface. That requires more investment. So always start private if you're still testing whether the app even works as intended.

What determines the price?

The cost depends on three things: complexity of the logic, number of integrations and whether the app needs its own backend. A simple tool that pulls data from Shopify and writes it to a CSV costs less than an app that synchronises in real time with an external API, processes webhooks and has its own interface.

Guide prices (always request a fixed quote):

• Internal tool without UI: €3,000–€5,000
• App with own admin interface and webhooks: €7,000–€12,000
• Public app with subscriptions and compliance: €15,000–€25,000

Always budget an extra 20–30% for maintenance and updates; Shopify's API changes regularly and your app must keep up.

How do you choose the right developer?

Look for someone who knows Shopify's ecosystem — not every web developer understands how Shopify's GraphQL Admin API, webhooks and app extensions work. Ask about previous Shopify apps (public or private), and check whether they give advice rather than blindly building what you ask for. Sometimes a smart API integration is more effective than a full app.

I work with one concrete proposal per project myself: fixed scope, fixed price, fixed timeline. No hourly billing and no surprises. If halfway through it turns out a feature isn't needed after all, I remove it and adjust the price — protecting your budget is more important than selling extra features.

From idea to working app

A good process looks like this:

1. Intake and scope — you explain the problem, I propose what belongs and doesn't belong in version one.
2. Quote — fixed price, fixed timeline, concrete deliverables.
3. Development in sprints — every 1–2 weeks a working component, so you give feedback along the way.
4. Test and go-live — installation in your shop, instruction for your team, technical documentation.

After delivery I remain available for maintenance and updates — no app is ever truly finished.

Want to build a custom Shopify app?

At Kattenberg 118 Studio I build both private custom apps and public Shopify apps, always with a fixed scope and price. I think along about what is and isn't necessary, and protect your budget — no commercial interest in complicated solutions, only in solutions that work.

Want to know more or get a concrete proposal? See /studio or send an email.