Shopify app development: when the app you need doesn't exist.

A custom app is installed in your store only and built around your processes. A public app is listed in the Shopify App Store and runs in many stores. The key difference: if an app contains Shopify Functions, it only runs as a custom app on Shopify Plus — as a public app it runs on every plan.

For merchants without Plus, that means checkout or payment logic comes in through a public app. That's exactly why I build my own App Store apps. Custom apps without Functions — for integrations, data sync or admin tools — run on every plan.

See my apps →

Shopify Functions are small programs that Shopify itself runs at checkout: they calculate discounts, hide payment or delivery methods or validate the cart. They replace Shopify Scripts, which could no longer be edited from 15 April 2026 and stopped running entirely on 30 June 2026.

If you're missing logic from old scripts, a report in your Shopify admin lists the scripts that were active. I rebuild that logic as a Function. Checkout Extensibility, Shopify's toolkit for visible checkout extensions, adds notices or fields — though on the information, shipping and payment steps only on Plus.

Hiding, reordering or renaming payment methods and controlling delivery options by rule all run on Shopify Functions — and therefore on every plan, as long as the logic comes from a public app. Shopify's own Checkout Blocks only offers payment rules on Plus.

For the most common cases there's my app KM Payment Rules — for example bank transfer for domestic orders only, or hiding PayPal above a certain cart total. If your rule goes further, a custom solution is a good topic for an intro call.

KM Payment Rules →Guide: hide payment methods →What works without Plus? →

Shopify now includes core B2B features on every plan: company profiles, payment terms, quantity rules and up to three catalogs with their own prices. Catalogs for individual companies, unlimited catalogs, deposits and partial payments remain Shopify Plus only.

Often a smaller solution is enough: invoice payment for trade or returning customers only works on every plan with a customer tag and a payment rule. Anything beyond that — approval workflows, prices from the ERP, tiers per customer group — I build as a custom app.

Guide: payment methods for B2B customers →

Middleware is a small program between Shopify and another system — ERP, inventory or ticketing. It translates data in both directions, catches errors and keeps logic out of Shopify that doesn't belong there.

Without Plus it's often the right approach: if the checkout can't be customised, the logic runs outside Shopify and only delivers results to the store — availability or links, for example, via metaobjects, Shopify's own objects for structured content.

Shopify Development →

Yes, as a partnership. If you have the expertise for a niche but no development team, I build the app for the Shopify App Store — with a revenue share instead of the full project price if you prefer.

That's how M&N Gewährleistungslabel Pro is being built right now, together with Luis Nickel of the e-commerce agency Herzog & Nickel. We agree the terms in a conversation — they depend on effort, market potential and who does what.