Shopify

Theme, app or Function? Where a Shopify change should live

Use the least code that does the job. Try a setting first, then the theme, then an existing app, then a custom app, and use a Function only when checkout logic really has to change. Each step down that list costs more to maintain.

By itmarkerz Technologies. Updated 30 October 2026.

The options, cheapest to maintain first

Where a Shopify change can live, and the trade-offs of each
Layer	Good for	Costs you	Limits
Admin settings	Shipping, tax, markets, basic discounts	Nothing but learning it	Only what Shopify offers
Theme	Anything customers see on the storefront, except parts of checkout	Merges when you update the theme	Can’t change how checkout calculates
Public app	Common needs: reviews, subscriptions, bundles	Monthly fee, and scripts that can slow pages	Their roadmap, not yours
Custom app	Your own integrations, admin screens and automation	Build and maintain it, and keep its API version current	API limits
Function	Rules in the cart and checkout: discounts, delivery, payment, validation	Build and maintain it; specialist skills	Custom ones need Plus; strict run limits

Common requests, and where we would put them

Common Shopify requests and the layer that usually suits each
Request	Usually lives in	Why
Change the look of a product page	Theme	Display only, with no business logic
Show a delivery estimate	Theme, or an app if it needs a carrier	Check accuracy before you promise a date
Wholesale tiers by customer	Function on Plus, or a public app	Price logic must hold at checkout, not just on the page
Hide a payment method for some orders	Function (payment customization)	A theme can’t enforce this
Stop an order under a minimum	Function (validation)	Client-side checks can be bypassed
Send orders to your ERP	Custom app, or a connector	A server-side integration job
Staff screen for approving something	Custom app	Runs outside the storefront
Product filters and search	Theme settings and a Shopify or public app	Common enough not to build

The rule behind the table is that if it must be true, not just look true, it can’t live only in the theme. Code in a theme runs in the customer’s browser, so a minimum order enforced only by a disabled button isn’t really enforced.

Questions before you approve any code

Does Shopify do this now? The platform moves fast, so a custom build from two years ago may have a native replacement.
What does this cost in year three? A cheap custom feature still needs updates. Five small apps at a monthly fee add up, too.
What does it do to page speed? Each app can add scripts to your storefront. Measure before and after.
What happens during your biggest sale? Check any app or API in the order path under load, and find out what fails if it goes down.
What happens if you uninstall it? Some apps leave code in your theme behind them, so ask how clean-up works.

Where to read next

For checkout rules, see Functions now that Scripts have gone. For a server-side integration, see the Shopify ERP integration guide. Our Shopify service page covers how we work on stores.

Questions

What is a custom app, and how do we get one?

It is an app made for one store, and it isn't listed on the App Store. Shopify says you now create and manage custom apps in the Dev Dashboard. Legacy custom apps made before January 1, 2026 are still managed from the Shopify admin.

Who should own the app and theme?

Your business should. Keep the store's admin and the developer access under accounts you control, and keep the theme code in a repository you can reach. Ask about this before work starts with any supplier.

Have a list of Shopify changes?

Send us the list, your store's address and your plan. We will tell you where each change should live, and whether it needs Plus.

Start a conversation Shopify development

We reply within one business day (IST).