# Custom Apps & Extensions

Custom Shopify apps and extensions add features your store needs that no off-the-shelf app provides. FleekApps builds private and public Shopify apps, Shopify Functions, checkout UI extensions, theme app extensions and admin extensions, the same way we build and ship our own apps, FunctionFlow AI and SmartSort AI.

- Provider: [FleekApps](https://fleekapps.com/)
- Start a project: https://fleekapps.com/contact/?service=custom-apps-extensions

## What’s included

- **Custom (private) apps:** Apps built for one store or organization: internal tools, admin workflows and integrations that fit how you work.
- **Public App Store apps:** Embedded apps with App Bridge, Shopify Billing, GDPR webhooks and everything needed to pass App Store review.
- **Shopify Functions:** Discount, delivery, payment, validation and cart transform functions in Rust or JavaScript, compiled to WebAssembly.
- **Checkout & account UI extensions:** Custom fields, upsells, banners and loyalty blocks in checkout, Thank you and customer account pages.
- **Theme app extensions:** App blocks and embeds merchants add in the theme editor, with no theme code edits.
- **Admin extensions & Flow:** Admin actions, blocks and Shopify Flow triggers and actions that bring your logic into the Shopify admin.

## Who it’s for

- **Merchants with unique workflows:** Your process does not fit an existing app, or you are paying for five apps to do one job.
- **Agencies and partners:** You need a dependable app team for a client build or extension.
- **Founders with an app idea:** You want to launch a public Shopify app with people who have done it.

## How we work

1. **Discover:** We learn your store, numbers, stack and goals, then agree what success looks like and how we will measure it.
2. **Design:** Flows, interfaces and architecture, reviewed with you before a line of production code is written.
3. **Build:** Short cycles with working previews on a development store, so you see progress every week.
4. **Launch:** QA on real devices and real checkouts, a rollout plan, and monitoring from day one.
5. **Grow:** We measure the result, then iterate: experiments, automations and new features on a monthly rhythm.

## Tools & platforms

Shopify CLI, App Bridge, Polaris, Shopify Functions, Rust, WebAssembly, Remix, Laravel, Vue, Admin GraphQL API, Billing API

## Related FleekApps apps

- [FunctionFlow AI](https://fleekapps.com/apps/functionflow-ai/): Discount, shipping, payment and checkout validation rules, built visually or described in plain English.
- [SmartSort AI](https://fleekapps.com/apps/smartsort-ai/): Automated collection sorting for Shopify: best sellers up, sold-out down, new arrivals and featured products in the spotlight.

## FAQ

### What is the difference between a custom app and a public app?

A custom app is built for a single store or organization and is not listed on the Shopify App Store. A public app is listed on the App Store, can be installed by any merchant, and has to pass Shopify’s review. We build both.

### Do custom apps with Shopify Functions need Shopify Plus?

Yes. Only stores on Shopify Plus can use custom apps that contain Shopify Functions. Stores on any plan can use public apps that contain Functions, which is why FunctionFlow AI works on every plan.

### Who owns the code?

You do. Custom work is delivered in your repository, with documentation and deployment instructions.

### Can you help us get a public app approved?

Yes. We have taken our own apps through the App Store requirements: embedded App Bridge apps, session-token auth, Shopify Billing, mandatory GDPR webhooks and listing assets.

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Source: https://fleekapps.com/services/custom-apps-extensions/