Custom Shopify App Development —
Private Apps, Public Apps & Extensions
From private ERP integrations to public App Store products, Checkout UI Extensions to Shopify Functions — we build every type of Shopify app using the official Remix stack and the latest Shopify APIs.
What Type of Shopify App Do You Need?
Every app type has different use cases, technical requirements, and timelines. We help you choose the right approach before writing a line of code.
Private Shopify Apps
A private app connects to a single Shopify store via the Admin API. Perfect for custom integrations (ERP, WMS, CRM), internal tooling, bespoke automation, or functionality your store needs that no public app provides. No app review required — faster to ship.
Examples
- ✓ERP / inventory sync (SAP, Tally, Zoho)
- ✓Custom order management dashboard
- ✓WhatsApp notification triggers
- ✓Custom pricing engine via Metafields
- ✓Vendor portal for product uploads
Public Shopify Apps
A public app can be installed by any Shopify merchant via the App Store or a direct install link. Built with OAuth 2.0, embedded in the Shopify Admin using App Bridge, and deployed on scalable Node.js infrastructure. We handle the full Shopify Partner review submission.
Examples
- ✓Niche automation tools
- ✓Industry-specific reporting apps
- ✓Loyalty/referral widgets
- ✓B2B pricing & wholesale apps
- ✓Custom shipping rate calculators
Checkout UI Extensions
Embed custom React components directly inside the Shopify Plus checkout flow — without touching checkout.liquid. Add upsells, delivery date pickers, gift messages, loyalty point displays, and trust badges at specific checkout steps.
Examples
- ✓Post-purchase upsell blocks
- ✓Delivery date picker widget
- ✓Gift message input field
- ✓Loyalty points display at checkout
- ✓Urgency countdown timers
Shopify Functions
Override Shopify's core platform logic — discounts, payment methods, delivery methods — with your own serverless functions compiled to WebAssembly. The most powerful way to customise Shopify's commerce engine without workarounds.
Examples
- ✓BOGO & bundle discount logic
- ✓Tiered / volume pricing
- ✓Hide COD above order threshold
- ✓Custom delivery filtering by postcode
- ✓B2B-specific discount rules
Admin UI Extensions
Extend the Shopify Admin with custom blocks on order detail pages, product pages, and customer profiles. Display live data from your warehouse, add quick-action buttons, show custom metafield editors, or embed third-party integrations directly in the merchant admin.
Examples
- ✓Order detail fulfillment widget
- ✓Product ERP sync status block
- ✓Customer loyalty tier display
- ✓Metafield editor UI
- ✓Custom B2B order notes panel
Theme App Extensions
Add custom storefront sections and blocks to any Shopify theme without modifying the theme's codebase. Merchants can drag and drop your extension blocks into any page using the Theme Editor. Compatible with all Online Store 2.0 themes.
Examples
- ✓Custom product badges app block
- ✓Review widget section
- ✓Countdown / urgency banner
- ✓Custom announcement bar
- ✓Wishlist button block
Private vs Public vs Checkout Extensions
| Dimension | Private App ✦ | Public App | Checkout Ext. |
|---|---|---|---|
| Scope | Single store only | Any Shopify merchant | Plus merchants only |
| App Store listing | No — direct install | Yes — discoverable | No — Plus only |
| OAuth required | No — API key + token | Yes — full OAuth 2.0 | Shopify Plus partner |
| Shopify review | No | Yes — 2–4 weeks | Yes — extension review |
| Best for | Internal tools, ERP sync | SaaS, sellable apps | Custom checkout logic |
| Revenue model | One-time build fee | Monthly subscriptions | Part of Plus project |
How We Build Your Shopify App
App Scoping & API Design
We define exactly which Shopify APIs your app needs (Admin API, Storefront API, Webhooks, GraphQL subscriptions), which extension points are required, and how data will flow between Shopify and any external systems. We produce a written technical spec before any development begins.
Remix App Setup & Auth
We scaffold the app using Shopify's official Remix template with the Shopify CLI. OAuth 2.0 installation flow, session storage (PostgreSQL or Redis), and App Bridge embedding are configured from day one. API version is locked to the latest stable release.
Core Feature Development
Feature development in two-week sprints with progress updates. We use Shopify's GraphQL Admin API (latest 2025-04 version), with Polaris for Admin UI components and App Bridge for authenticated iframe communication. All webhooks are verified with HMAC.
Extension Development
Checkout UI Extensions built with React and Shopify's extension API. Shopify Functions written in Rust or JavaScript. Theme App Extensions scaffolded with the CLI. Each extension type goes through Shopify's extension-specific testing requirements.
Testing, Submission & Launch
Full QA on development stores and Partner sandbox. For public apps: Shopify Partner review submission with documentation, privacy policy, and test account. For private apps: staging deployment and load testing. Post-launch monitoring and 30 days of included support.
Our Shopify App Technology Stack
What Our App Clients Say
"Sigill built a custom private app that syncs our Tally ERP with Shopify in real time — products, inventory, and orders both ways. It replaced 4 hours of daily manual work and has been running without issues for 8 months."
"We had a very specific B2B pricing requirement that no public app could handle. Sigill built a custom Shopify Function that applies tiered pricing based on customer tags and order value. It works exactly as we specced."
"Our custom checkout extension — an upsell block that shows complementary products at the shipping step — increased our average order value by ₹340 within the first two weeks. The Sigill team delivered it in three weeks, start to finish."
Frequently Asked Questions
A private app connects to one specific Shopify store using an API key. It doesn't go through the App Store or require OAuth. A public app uses OAuth and can be installed by any merchant. Private apps are faster to build and deploy; public apps can be monetised and discovered on the App Store. We recommend private apps for internal integrations and public apps when you want to sell the functionality to other merchants.
A simple private app (ERP sync, webhook processor, basic admin UI) typically costs ₹80,000–₹2,00,000. A public app with full OAuth, billing, and a polished Polaris UI typically costs ₹2,50,000–₹6,00,000. Checkout UI Extensions are scoped individually at ₹60,000–₹1,50,000 per extension. All projects are fixed-price.
We always build on the latest stable Shopify API version — currently 2025-04. We pin the API version explicitly in every app, which means your app won't break when Shopify releases new versions. We also offer an annual API version update service to keep apps on the latest stable version.
Yes — we use Shopify's official Remix template (create-shopify-app) for all new public and private apps. It includes OAuth handling, session storage, App Bridge setup, and Shopify CLI integration out of the box. Remix is Shopify's recommended framework for app development as of 2024.
Yes. We prepare the full Partner submission package: app listing copy, screenshots, privacy policy, required webhooks (GDPR mandatory), app review account, and test store credentials. Shopify's review typically takes 2–4 weeks. We handle any review feedback and resubmission.
Shopify Functions are serverless programs that replace Shopify's built-in commerce logic. You need them when you want custom discount logic (BOGO, bundle discounts, tiered pricing), custom payment method filtering (hide COD above ₹X), or custom delivery method rules. They require Shopify Plus and run at the edge — no latency penalty.
Yes — most private apps exist specifically to bridge Shopify with an external system. We've built integrations with Tally ERP, Zoho CRM, SAP, WMS systems, WhatsApp Business API, custom fulfilment partners, payment reconciliation tools, and more. We use Shopify webhooks for real-time data and scheduled cron jobs for bulk sync.
A simple private app with 2–3 endpoints takes 3–5 weeks. A Checkout UI Extension takes 2–4 weeks. A full public app with Admin UI, billing, OAuth, and Polaris takes 6–12 weeks depending on feature count. We provide a detailed timeline in the proposal.
Yes — we offer monthly retainer support covering API version updates, bug fixes, new feature development, performance monitoring, and Shopify platform change responses. Shopify releases new API versions quarterly, and deprecated API versions are sunset after 12 months, so ongoing maintenance is important for app longevity.
Yes and this is one of the most common requests we get. Merchants running multiple conflicting apps, or paying ₹5,000–₹15,000/month in app subscriptions, often find it more cost-effective to replace two or three apps with a single custom private app built specifically for their store. We audit your current app stack and recommend what makes sense to replace.
Tell Us What Your App Needs to Do
Describe the problem you're trying to solve — we'll recommend the right app type and send a fixed-price proposal within 24 hours.