How to choose a Shopify Hydrogen agency: a checklist

Choosing a Shopify Hydrogen agency means hiring a team that can build and run a headless storefront on Shopify's own stack, Hydrogen on Oxygen, fed by the Storefront API, with Shopify still handling checkout. This checklist is for founders, ecommerce leads and operators who need to compare agencies on evidence rather than on logos, and who want to know what to ask before they sign.

Start with the decision, not the directory

Lists of the best Shopify agencies are useful for one thing: finding names. They are useless for ranking them. Directory positions reflect review volume and listing spend, and a team with a long run of Liquid themes behind it can sit above a team that builds Hydrogen storefronts and runs them every week. Treat any list of top Shopify agencies as a long list, not a verdict.

Hydrogen is a different job from theme work; our Shopify Hydrogen development page describes what that job contains. Before you compare agencies, decide what you are buying: a one-off build, a build with a migration from an existing theme, or a build plus the team that owns the storefront afterwards. The third is the one most brands actually need.

Two useful definitions before the criteria. Shopify Hydrogen is Shopify's React-based framework for building headless storefronts on top of Shopify's Storefront API; current versions are built on React Router (formerly Remix). As of the 2026-10 release Shopify describes Hydrogen as a headless toolkit that you add to a framework of your choice, with the React Router 7 template as the default path to Oxygen hosting. Headless (headless Shopify / headless commerce) means the storefront front end is decoupled from Shopify's back office and checkout and talks to Shopify through APIs; Shopify still runs products, orders, customers and checkout. If you are still deciding whether headless is right for your store, read Shopify Hydrogen vs Liquid themes first.

What a Shopify Hydrogen agency has to know

A Liquid theme is a conventional Shopify storefront built with Shopify's Liquid templating and the theme editor; the alternative to Hydrogen. In a theme, Shopify owns routing, rendering and hosting. In Hydrogen, the agency owns routing, rendering, data loading and UI, and Shopify provides the Storefront API, the Customer Account API and checkout. That shift is why the agency choice matters more than it does for a theme.

How to judge Hydrogen depth

Ask the team to explain each of the following in their own words. The quality of the explanation tells you more than the answer.

• Hydrogen versus a Liquid theme. A strong team can name the cases where a well-built theme on Online Store 2.0 (JSON templates, sections and blocks) is the better choice. "Always headless" is a sales position, not advice.
• Oxygen. Oxygen is Shopify's global edge hosting for Hydrogen storefronts, included with Shopify plans; deploys from Git. Every deployment is an immutable snapshot with its own preview URL, and a rollback points the environment back at an earlier one. The team should explain all three without notes.
• The Storefront API. The Storefront API is Shopify's GraphQL API that a headless storefront uses to read products, collections, carts and customer data. Ask how they cache it and how they handle API versioning: versions are dated and released quarterly, and a storefront that never upgrades eventually breaks.
• The Customer Account API. Shopify's API and passwordless login for customer accounts in headless storefronts. Ask whether they have built an account area with orders, addresses and a store-credit balance on it.
• Checkout. Checkout stays Shopify-hosted in every Hydrogen build; anyone who promises "headless checkout" misunderstands the platform. Checkout extensions / checkout extensibility are Shopify's supported way to customise checkout (UI extensions, branding API, Shopify Functions) without editing checkout.liquid; checkout itself stays Shopify-hosted. checkout.liquid is deprecated and no longer supported. Extensions on the information, shipping and payment steps are available to stores on Shopify Plus only.
• Shopify Plus. Shopify Plus is Shopify's enterprise plan with higher limits, checkout extensibility, Shopify Functions, B2B and Markets features. A team with real Plus experience can describe a Shopify Function they have scoped and the limit they hit doing it.
• Legacy Hydrogen. Storefronts on Hydrogen 2026-04 and earlier are what Shopify now labels Legacy Hydrogen, with its own migration guide to the current release. Ask whether the team has migrated one.

The checklist

Score each agency on these ten points. Ask for evidence.

1. Live Hydrogen storefronts you can open. Not mockups, not "in development". A storefront on Shopify's stack reports Shopify, Oxygen and Hydrogen in its powered-by response header.
2. Named people. Who writes the code, who reviews it, and who answers after launch. A senior person on the pitch who disappears after signature is the oldest pattern in agency work.
3. Honesty about platform limits. What checkout cannot do, which app has no headless integration, which request is better deferred.
4. A migration plan with a redirect map. URL mapping, 301 redirects, structured data and metadata carried over, indexation monitored after launch.
5. Analytics owned end to end. Pixels in code rather than in a tag-manager container, an event taxonomy written before launch, attribution verified from storefront to checkout with test orders.
6. A design system, not page-by-page design. Reusable components, typography and spacing rules, so new pages can be composed without starting from zero.
7. Integrations built into the storefront. Reviews, helpdesk chat, returns, store credit and inventory sync integrated into the Hydrogen code, not bolted on with scripts.
8. A staging environment and a preview link for every change. Oxygen gives every deployment a preview URL; an agency that skips the step is skipping QA.
9. Maintenance as a standing item. Framework, package and Shopify API version upkeep scheduled monthly, so the storefront does not quietly break between projects.
10. An after-launch model you understand. Who you message, how requests are prioritized, what is covered and what is scoped separately.

Questions to ask on the first call

Bring these to every agency and compare the answers.

• Which of your live Hydrogen storefronts is closest to our catalog and our team size, and may we speak to that client?
• Who on your team will work on our store, and what else are they working on?
• When was the last time you advised a brand not to go headless, and why?
• How do you handle a request from our customer-care team on a weekday evening?
• What breaks most often on a Hydrogen storefront after launch, and how do you prevent it?
• How do you test a change before it reaches production?
• How do you verify that attribution survives the move from the storefront to checkout?
• What do you do when a third-party app has no headless integration?
• How do you price, and what changes the price? Listen for a process, not a package.
• What does your retainer cover, and what would you refuse to do under it?

If you want to hire Shopify Hydrogen developers rather than an agency, the same questions apply. Add one more: who reviews their code, and who covers when they are away.

Red flags

One of these is a reason to slow down. Two is a reason to walk.

• A published price list for a storefront nobody has seen yet.
• "Headless checkout" as a feature.
• No live storefront on Oxygen, or a portfolio that is all Liquid themes with Hydrogen added to the services page.
• Case studies made of adjectives and percentages with no description of what was actually built.
• A junior team behind a senior pitch, or developers you are not allowed to talk to.
• A vague answer to how they test before production.
• A support model that is a ticket queue with no named owner.
• Partner badges or tiers that cannot be verified.
• Guarantees of rankings, uplift or zero downtime. Nobody controls all three.

How to read a case study

Case studies are written to be read quickly. Read them slowly.

• Look for scope, not results. A useful case describes product systems, cart behavior, account areas, markets, content model and integrations. Percentages without context describe the client's ad budget, not the agency's craft.
• Check that the storefront is live and still on the stack. Open it and look at the powered-by header. If it has moved back to a theme, ask why.
• Find the after-launch paragraph. The best cases describe what the agency does now: launches, tests, fixes, analytics. If the story ends on launch day, so did the relationship.
• Separate client work from concept work. Concept stores show design range when labeled as such. They are not evidence of running a storefront under real traffic.
• Look for the hard parts. A credible case admits what Shopify would not allow, what was deferred, and what the team would do differently.
• Match the catalog shape to yours. A storefront built around colorways and product systems is different work from one built around a deep catalog with many variants. Pick the agency whose hard problems resemble yours.

Three kinds of agency

Most agencies fit one of three models. The trade-offs are real.

Body shop

• What you buy: hours against tickets
• Who you talk to: a queue
• After launch: the next ticket
• Requests from marketing, support or logistics: each becomes a ticket to be estimated
• Context carried between requests: none
• Cost: lowest per hour
• Fits: small, well-specified tasks

Project agency

• What you buy: a defined build, then a hand-off
• Who you talk to: a project manager
• After launch: a separate support contract, often with another team
• Requests from marketing, support or logistics: out of scope
• Context carried between requests: lost at hand-off
• Cost: fixed per project
• Fits: brands with an in-house team to take over

Embedded partner

• What you buy: a build, then the team that runs the storefront
• Who you talk to: a named senior person
• After launch: the same people, on a monthly retainer scoped per client
• Requests from marketing, support or logistics: closed by the people who know the codebase
• Context carried between requests: kept, including why the color logic works and which test is running
• Cost: highest, and the one that pays back in kept context
• Fits: brands without an in-house storefront team

Where 21phi stands

21phi is a Shopify Partner with Shopify Plus experience, based in Toronto and working with brands across North America. We are the third kind. We build Hydrogen storefronts and then stay as the embedded team behind them: the agency works inside the client's channels and roadmap as the storefront, analytics and growth team, on a monthly retainer scoped per client. How we work describes the engagement, and Shopify support and maintenance describes what the retainer covers.

In practice that looks like this. We sit in the client's own group chats for web, customer care and the wider team, and questions from any teammate are answered there directly, by a named senior person. Requests come from every department and all of them land with us: a final-sale label from customer care, a speed check from logistics, a pricing display from operations, a landing page from marketing, a navigation change from the founder. Urgent fixes go to the front of the queue. A weekly analytics review, run by us, walks the client through what changed in the funnel and what to test next. Maintenance is a standing monthly item. When a third-party app misbehaves, we are the team that chases the vendor. And we tell clients what Shopify's hosted checkout can and cannot do before the build, not after.

This costs more than a body shop, and it should. A body shop bills for tasks and forgets your store between tickets, so every request starts from zero. An embedded partner carries the context, which is why fixes are fast, why integrations hold, and why the storefront keeps improving instead of slowly breaking. It pays because the people who built the store are the ones fixing, measuring and extending it.

Score us against the checklist like anyone else. Our storefronts are open: AsWeMove, a Shopify Plus apparel brand on Hydrogen that we built and continue to support; Kayusha, a Shopify Hydrogen storefront 21phi designed and built for Kayusha, a premium pet-carrier brand; and Éva Blanc, a 21phi concept store, labeled as one. Our case studies describe scope rather than percentages, and the people on the first call are the people who do the work.

Next step

If you are evaluating a headless build or looking to hire Shopify Hydrogen developers who stay after launch, start with Shopify Hydrogen development to see how we scope and build, then tell us about your store. Every project is scoped individually, so expect questions back, not a package.