Shopify app development for the logic no app listing covers.
Custom apps for one store, public apps for the App Store, embedded admin tools, Shopify Functions and checkout extensions, and the integrations and agents that work through them. Built on the current GraphQL Admin API, kept current as Shopify ships a new API version every quarter.
What a Shopify app development team should build, and what it should talk you out of.
A Shopify app is code that runs outside the store and works on it through Shopify's APIs and extension points. Most merchants need one of three things: a custom app that does one store's business logic (pricing rules, order routing, a sync with the ERP), a public app sold to many merchants through the Shopify App Store, or a set of extensions (Functions, checkout UI extensions, admin blocks) that change how Shopify itself behaves. Gigabit builds all three. A senior engineer owns the design; AI agents take the repetitive work such as typed GraphQL queries, tests and the quarterly API upgrade. Before any of it, we check whether an existing app already does the job, because often one does.
The platform rules decide the architecture, so we start with them (read on shopify.dev on 24 October 2026). The REST Admin API has been legacy since 1 October 2024, and since 1 April 2025 new public apps must use the GraphQL Admin API only. Shopify releases an API version every three months and supports each for at least 12 months, so every app needs an upgrade path. A custom app installs on one store, or on stores in one Shopify Plus organization, and cannot later be switched to public distribution. Custom apps that contain Shopify Functions run only on Plus stores, and checkout UI extensions on the information, shipping and payment steps are Plus only too. Gigabit is a Shopify Partner.
The Shopify apps and extensions we build.
The store itself, theme work and migrations sit on the Shopify platform page. This is the app layer underneath.
Custom apps for one store
Business logic for a single store or a Plus organization: pricing and inventory rules, order routing, bulk operations on the catalog, built on the GraphQL Admin API with webhooks instead of polling.
Public apps for the App Store
Multi-tenant apps with OAuth on install, session tokens, the Shopify Billing API for charges and an embedded admin built on App Bridge, prepared against the App Store requirements before submission.
Embedded admin tools
App pages inside the Shopify admin plus admin actions, admin blocks on product, order and customer pages, and print actions for invoices or packing slips, so staff never leave the admin.
Functions and checkout extensions
Discount, delivery, payment, cart transform and cart validation logic as Shopify Functions compiled to WebAssembly, and checkout UI extensions for fields, upsells and messages. Includes rebuilding Shopify Scripts, which stopped running on 30 June 2026.
Integrations
Two-way sync between Shopify and the ERP, WMS, PIM, helpdesk or marketplace, with idempotent writes, retries, reconciliation counts and an alert when a record fails.
Agents that act through the app
Support, returns and back-office agents that read live order data and take actions through scoped API access, with a confidence threshold and a human approval step where a mistake costs money.
Scope, build, review, keep current.
Scope
Decide custom or public, which extension points and API scopes the app needs, and whether Plus is required. It ends in a written fixed price.
Build
Two-week sprints on a development store, with a demo every Friday. GraphQL queries are typed and cost-checked against Shopify's rate limits.
Launch
Custom apps install straight on your store. Public apps go through App Store review with test credentials, a screencast and a listing that makes no claims the app cannot back.
Keep current
Each quarter's API version is tested before the one you are on is retired, and webhooks, scopes and extensions are checked against the changelog.
Published prices, mapped to the job.
Every price here is the same one on the pricing page. Work with no published price gets a fixed price in writing before it starts.
Figures in the notes are what past clients paid, from the published case studies; they show the range, not a rate card. Work with no natural end, such as ongoing development, is priced per engineer per month with no lock-in.
When to hire us for this, and when not to.
- Your rules for pricing, fulfilment or B2B ordering are specific enough that no App Store listing fits without workarounds.
- Staff copy data between Shopify and another system every day.
- You want to sell an app to other merchants and need it to pass App Store review the first time.
- You are on Shopify Plus and need checkout or Functions logic the platform does not ship.
- A well-reviewed public app already does it. Install that first; it is cheaper than any build.
- You need a theme change or a new store. That is a Store Build; see the Shopify platform page.
- You need custom checkout steps or a custom Function in a private app but are not on Plus. Price the upgrade, or look for a public app that ships the Function.
Work on Shopify's APIs in production.
A support agent with API access to a Shopify Plus store's live orders and a nightly catalog sync, which starts returns, applies discount codes and updates addresses with the customer's confirmation. It is a private integration, not a public app.
A confidence-gated AI support agent now resolves 64% of tickets autonomously, cutting support costs 62% — $217,200 saved in year one.
These are past engagements at the prices those clients paid. For build price, monthly cost and payback side by side, see what ten client projects cost.
Shopify app development, answered
How much does Shopify app development cost?
It depends on the extension points, the systems the app talks to and whether it is public. A custom or public app is a fixed price in writing after scoping; the project costs page shows what past builds cost. One integration or automated workflow on the Admin API is the AI Quick Win Sprint, $8,000 fixed over 3 weeks for up to three tools. A production agent is a flat fee from $8,000, ongoing development runs on an embedded team at $3,000–$7,500 per engineer per month, and monitoring after launch starts at $3,000 a month.
Should we build a custom app or a public app?
Build a custom app when the logic belongs to your business: it installs on one store or the stores in one Plus organization, needs no App Store review and cannot charge through Shopify's billing. Build a public app when you want to sell it to other merchants: it needs App Store review, Shopify's Billing API for every charge and an embedded admin built on App Bridge. Shopify does not let you change the distribution method after you choose it, so decide before the build (rules checked on shopify.dev on 24 October 2026).
Can you still build Shopify apps on the REST Admin API?
Shopify calls the REST Admin API legacy as of 1 October 2024, and every new public app since 1 April 2025 must use the GraphQL Admin API only. We build on GraphQL and migrate older apps off REST, which also removes the risk of an endpoint disappearing in a future version.
Do we need Shopify Plus for a custom app?
Not for a custom app in general. You do need Plus for two things in a private app: custom apps that contain Shopify Functions run only on Plus stores, and checkout UI extensions on the information, shipping and payment steps are Plus only. Public App Store apps that include Functions work on any plan. Our Shopify vs Shopify Plus comparison has the price side.
How do you keep an app working when Shopify changes its API?
Shopify releases a new API version every three months and supports each one for at least 12 months; a call to a retired version falls forward to the oldest supported one, which can change behaviour without warning. We pin the version, test the next one on a development store each quarter, and upgrade before the old one is retired.
Can an AI agent work through a Shopify app?
Yes. An agent can read orders, customers and products and take actions through the same scoped API access an app uses, with order webhooks telling it when something changes. In our published deployment the agent starts returns, applies discount codes and updates addresses only with the customer's confirmation, and replies on its own only above a confidence threshold. Shopify also publishes protocols and MCP servers for agents that build carts and check out on a buyer's behalf.
Often scoped alongside.
Shopify development
Store builds, migrations, apps and agents on Shopify and Shopify Plus.
Shopify developmentERP and API integration
Orders, stock and invoices in sync between Shopify and the ERP.
ERP and API integrationGigabit Agents
Production AI agents for a flat fee, grounded in live store data.
Gigabit AgentsFrom the field notes
Need Shopify to do something it doesn't?
Describe the rule, the workflow or the app you want to sell. A senior engineer replies with whether an existing app already does it, and if not, how we would build it and the fixed price.