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FREELANCE SHOPIFY DEVELOPER · SINCE 2016

Custom Shopify development for merchants who outgrew the theme.

I build complete Shopify stores — and the parts most agencies pass on: ERP and systems integrations, headless storefronts, custom apps and the catalogue logic your business actually needs. One developer, start to finish.

Tell me what you’re building → See the work

Reply within one business day. The first conversation costs nothing.

What I’m usually called in for

  • SHOPIFY SINCE 2016
  • SHOPIFY PLUS
  • ERP INTEGRATIONS
  • HYDROGEN
  • CUSTOM APPS
  • MIGRATIONS

Sound familiar?

These are the sentences I hear most often on a first call. If one of them is yours, I know what to do about it.

“The platform is holding us back.”

You want a new feature, a different layout or a connection to a system you already run — and you hit a ceiling with nothing behind it.

“The store is slow and nobody knows why.”

Three years of accumulation: twelve apps, a theme nobody wants to open, and a Core Web Vitals report that only ever goes one way.

“Our stock is wrong by the time the warehouse sees it.”

Inventory lives in an ERP, orders live in Shopify, and somebody re-types the difference. Oversells and refunds are the tax you pay for that.

“We are afraid of losing Google if we replatform.”

Replatforming risk is URL mapping and redirects. That work happens before the switch, not after it.

WHAT I BUILD

Everything around Shopify, from one developer

From a first store through a custom theme and custom apps to ERP and warehouse integrations. You do not need to line up three suppliers and hope they talk to each other.

Shopify store builds

A complete store, built properly from the start — information architecture, theme, product data, shipping, payments and launch. Built to grow, not rebuilt in eighteen months.

  • Design and front end in Liquid
  • Product and collection data modelling
  • Shipping, payments and tax setup
  • Launch checklist and handover
What a store really costs to run →

Migrations to Shopify

Moving from WooCommerce, Magento, BigCommerce or a legacy in-house platform without losing rankings, order history or customer accounts.

  • URL mapping and 301 redirects
  • Products, orders, customers, reviews
  • Redirect testing before switchover
  • Post-launch rank monitoring
Migrating without losing SEO →

Custom theme development

Clean Liquid and Online Store 2.0 sections your team can actually recombine — not a bought theme patched with five apps until it crawls.

  • Figma to Liquid, pixel-accurate
  • Online Store 2.0 sections and blocks
  • Work on an existing theme
  • Performance treated as a requirement
How a custom theme is built →

Shopify apps & extensions

Custom apps where the App Store stops. Admin extensions, checkout UI extensions, Shopify Functions, private apps and public listings.

  • Private and public apps
  • Checkout UI extensions and Functions
  • Admin blocks and dashboards
  • Audit of the apps you already pay for
Custom app or an app from the store? →

ERP & systems integration

Connecting Shopify to what the business already runs on. NetSuite, SAP, Dynamics, Xero, QuickBooks, 3PLs, CRMs — two-way, with real error handling.

  • NetSuite, SAP, Dynamics, in-house ERPs
  • Xero, QuickBooks, Sage
  • 3PL, WMS and courier systems
  • Retries, logging and alerting
How ERP integration actually works →

Headless & Hydrogen

React storefronts on the Storefront API when a Liquid theme genuinely stops being enough. And an honest answer when it doesn't.

  • Hydrogen and Oxygen
  • Storefront and Customer Account API
  • Custom front end, Shopify back end
  • A straight verdict on whether it pays
Is headless worth it for you? →

Speed & Core Web Vitals

A developer's speed audit. Not “install a speed app” — finding what is specifically slowing your store down, then removing it.

  • App and script teardown
  • Liquid and render blocking
  • Images, fonts and third parties
  • LCP, INP and CLS in the field
The speed audit I run →

Audits & consulting

A technical review or an hour of straight answers. A good place to start when you can't tell whether the problem is the platform, the theme or the apps.

  • Technical store audit
  • Pre-migration consultation
  • Second opinion on an agency quote
  • Training for your team
How to hire a Shopify developer →
BEYOND THE THEME

The work that starts where the App Store stops

Shopify is excellent at the standard store. The moment your business is not standard — wholesale pricing, fourteen markets, a warehouse system, a catalogue that does not fit a title and a price — you are outside what an app can configure.

That is the part I do. Not because bespoke is better, but because at some point it is the only thing that is honest.

Read how it gets built →

B2B and wholesale

Company accounts, price lists per customer, quantity rules, net terms and a wholesale experience that does not require a second store.

Multiple markets and currencies

Markets, currencies, translations and region-aware pricing, shipping and content — from one store, without a duplicate for every country.

Subscriptions and recurring orders

Subscription APIs, selling plans and the billing edge cases that decide whether recurring revenue is reliable or a support queue.

Warehouse, 3PL and ERP sync

Inventory that is right when the warehouse reads it, orders that reach finance, tracking that flows back. With retries, not hope.

Checkout logic

Shopify Functions for discounts, delivery and payment rules, plus checkout UI extensions — the supported way to change checkout on Plus.

Complex catalogue data

Metafields and metaobjects for products that do not fit a title-and-price model: configurable goods, specifications, bundles, technical data.

SELECTED WORK

Three I can point to publicly

A public sample, not the whole list — much of the work is under NDA or white-labelled through agencies.

Frost Form

frostform.com · Shopify Plus

Dual-market Shopify Plus build serving US and EU customers with region-aware pricing, shipping and content, plus an online course section that unlocks by purchased product and tags customers automatically.

Shopify PlusUS + EU marketsCustomer taggingTheme front end
frostform.com ↗

Artra

artra.com · 14 markets

A network of stores for one client across 14 markets. Full back-end setup through the Admin API, a custom data layer for analytics, and custom theme development.

Admin API14 marketsData layerCustom theme
artra.com ↗

Comfy

comfy.sk · storefront work

Advanced theme work on a live store — Liquid changes, custom sections and a sharper product experience, without rebuilding anything from scratch.

Advanced theme workLiquidCustom sections
comfy.sk ↗
Ask about something similar →

How a project runs

Four stages, no black boxes, no surprises halfway through.

01

Audit

We go through what you have, what is slowing you down and whether the change is needed at all. Sometimes the answer is to change nothing.

02

Scope & quote

A written scope: what gets built, what does not, what it costs and how long it takes. Including the unglamorous parts — redirects, error handling, data mapping.

03

Build

Work happens on a staging store with regular demos. You know where the project is without having to ask.

04

Launch & support

Launch outside peak hours, redirects verified, a real test order placed. Then I stay available — ad hoc or on a retainer.

ABOUT

I’m Mario. I’ve been building on Shopify since 2016.

I started where most people do — theme customisation and Liquid. Over nine years that turned into custom apps, headless storefronts and the integration work that keeps a growing store running: connecting Shopify to the systems a business actually runs on.

I’m a full-stack developer, not only a Shopify one. I studied and worked on projects in Denmark and I build software for international clients, mostly American. That combination is why I can take on the things a standard ecommerce agency stops at — an Admin API integration, a custom app, or a store that has to serve fourteen markets at once.

I work solo and ship complete features, not tickets handed back half-finished. Based in Copenhagen: full overlap with UK and Irish hours, and a working morning overlap with the US East Coast. If you are not sure whether what you need is even feasible, ask — I will tell you straight, including when the answer is that it is not worth it.

[email protected]
Mário Matejovič, freelance Shopify developer based in Copenhagen
Mário Matejovič Copenhagen

Frequently asked questions

The things people ask before hiring me — answered the way I’d answer them on a call, not the way a brochure would.

What does a custom Shopify developer do that an app cannot?
Apps solve problems that many stores share. A developer is worth paying for when the problem is specific to your business: your pricing rules, your ERP, your catalogue structure, your checkout logic. The rule of thumb I use is simple — if a well-reviewed app does 90% of it, install the app. If it does 60% and you would spend the rest of the year working around the other 40%, build it.
Do you work on stores somebody else built?
Yes, most of the time. The first step is usually an audit: I go through the theme, the apps and the integrations and write up what is fine, what is worth fixing and what you are paying for twice. You get that in writing whether or not you hire me for the fix.
How much does custom Shopify development cost?
It depends on the work, but honest ranges help more than a refusal to answer. Small scoped jobs — a section, a fix, a small integration — are usually a few days. A custom theme or a proper ERP integration is a multi-week project. A headless build is a multi-month one. I quote fixed prices against a written scope, so the number you approve is the number you pay.
Freelancer or agency — what is the difference in practice?
With an agency you get process, cover when someone is away, and a project manager between you and the person writing the code. With me you talk to the developer, decisions take minutes instead of a sprint, and there is no account-management margin on top. The honest trade-off is capacity: I take on work I can finish, and I say no when I cannot.
Will migrating to Shopify cost me my Google rankings?
It does not have to. What matters is mapping every old URL to a new one and deploying 301 redirects before the switch, not after. A short dip of a few percent is normal; positions usually recover within four to eight weeks. Anyone promising zero movement is guessing.
Custom theme or a paid theme?
Both are legitimate. A paid theme is a sensible choice for a smaller store with a standard catalogue and a tight budget. A custom theme pays off when the brand has its own design language, when you need something standard themes cannot do, and above all when you do not want to trade away performance to five apps that fake it.
Do I actually need a custom app?
Usually not, and I will say so. A custom app makes sense when you are solving a process specific to your company, when you would otherwise pay three separate app subscriptions to approximate it, or when you need to change checkout behaviour on Plus. Otherwise a good existing app is cheaper and better maintained.
Where are you based and which time zones do you cover?
Copenhagen. That means full working-day overlap with the UK and Ireland, most of the day with the rest of Europe, and a solid morning overlap with the US East Coast. I reply to email within one business day.

From the blog

160 articles on the harder end of Shopify — written the way I’d explain it on a call.

All articles →
Integrations

Shopify ERP integration: connecting NetSuite, SAP & Dynamics

Stock in the ERP, orders in Shopify, someone re-typing the difference. Here is how the connection is actually built — and where most of them quietly go wrong.

9 MIN · READ →

 Apps & checkout

Shopify custom apps vs third-party apps: how to decide

Install another subscription and bend your process to fit it, or build exactly what you need? How I decide — without the bias of only selling one of them.

8 MIN · READ →

 Headless & architecture

Headless Shopify with Hydrogen: when it's worth it (and when it isn't)

\"Should we go headless?\" is one of the most common questions I get. The honest answer is usually \"probably not yet\" — here is how to tell.

8 MIN · READ →
FREE FIRST CONVERSATION

Got a Shopify problem the App Store can’t fix?

Tell me what is broken or what you are trying to build. I read every message and reply within one business day — usually with questions or a first estimate attached.

[email protected]

Or just send the link to your store — I’ll take a look.