Most "how to choose a Shopify agency" articles talk about portfolios and price. Those matter, but they don't tell you whether the code you get will still work in two years. If you run a store in the US, UK, Canada or Australia and you're about to hire an agency (or you're the in-house developer asked to vet one), these are the technical questions I'd ask.
1. Do they build on Online Store 2.0 sections, or hard-code templates?
Modern Shopify themes use JSON templates and sections, so merchants can rearrange pages in the theme editor without a developer. Ask to see a recent theme. If every page layout is fixed in Liquid, every future change becomes a paid ticket.
2. How do they handle theme code: Git, CLI and Theme Check?
A good agency keeps the theme in Git, uses Shopify CLI to push to a development theme, and runs Theme Check (Shopify's linter, built into the CLI as shopify theme check) before release. Ask for a sample pull request. "We edit in the online code editor" is a red flag for anything beyond small fixes.
3. What is their stance on apps?
Every app adds scripts, and many leave code behind after they're uninstalled. Ask:
- Which apps would they remove, or replace with native features?
- Do they check theme files for leftover snippets after an app is removed?
- Will a custom app be built on Shopify's current APIs (the GraphQL Admin API), and who owns it?
4. Checkout: do they know Checkout Extensibility?
Checkout customisation now runs through Checkout UI extensions and Shopify Functions, not through editing checkout.liquid, which Shopify has retired. An agency that still promises checkout.liquid edits is out of date. Ask what they'd use for a delivery-date picker, a custom discount rule, or hiding a payment method for some customers.
5. Performance budget
Ask how they measure speed: Core Web Vitals field data, not one Lighthouse run. Ask what they do about large images, third-party scripts and app embeds, and ask for before/after numbers from a past project.
6. Accessibility
For UK, EU-facing and US stores, ask whether they test with a keyboard and a screen reader, and which WCAG level they aim for. A theme that fails keyboard navigation loses sales and invites complaints.
7. Migrations and SEO
If you're moving from WooCommerce, Magento or BigCommerce, ask for their redirect plan: a URL map, Shopify's URL redirect import, and a check of your top landing pages in Search Console after launch.
8. Handover
At the end you should get admin access that stays with you, the theme repository, app credentials in your name, and a short document of what was customised.
A quick scoring sheet
| Question | Good answer |
|---|---|
| Theme architecture | OS 2.0 sections, merchant-editable |
| Workflow | Git + Shopify CLI + Theme Check |
| Apps | Fewer apps, clean removal |
| Checkout | UI extensions + Functions |
| Speed | Field data, before/after numbers |
| Handover | Repo + docs + your ownership |
If you want to see how we answer these, here is Dzimark's Shopify development team page. We build for stores in the USA, UK, Canada and Australia.
FAQ
Is a Shopify Partner badge enough?
It shows the agency has a partner account. It doesn't show code quality, so still ask the questions above.
Should my agency edit the live theme?
No. Work should happen on a duplicate or development theme and be published after review.
Do I need Shopify Plus for checkout changes?
Checkout UI extensions on the information, shipping and payment steps are a Shopify Plus feature; the thank-you and order status pages can be extended on other plans. Check Shopify's current docs for your plan.
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