Search "best Shopify agency New York" and you will find the same seven or eight names shuffled into a different order every time. Most of these lists come from directories or app companies that have never opened a Shopify theme file. They rank agencies the way you would rank restaurants: by how nice the dining room looks, not by what is happening in the kitchen.
We pulled the top ranking articles for "Shopify CRO agency NYC" and checked what they actually measure. None of them look at page speed data. None of them check whether a site loads cleanly on an iPhone. None of them ask how many third-party apps are quietly slowing the checkout down. They rank on portfolio polish, client logos, and Clutch review counts. That tells you whether an agency can design a beautiful homepage. It tells you nothing about whether your site will actually convert.
For a Shopify Plus brand spending $30,000 to $200,000 a month on paid traffic, that gap is expensive. A redesign that adds two seconds to your load time will lose you more customers than it wins. So instead of another portfolio ranking, we built this list around five technical questions, then researched seven real New York Shopify agencies against them using only what each agency has publicly disclosed.
The 5-Question Technical Framework
Before you hire anyone, ask these five questions. If an agency cannot answer them clearly, they are likely going to redesign your storefront without fixing what is actually costing you sales.
1. Do they audit ghost scripts? Most Shopify stores run five to fifteen apps that are no longer used but still load on every page. An agency should be able to name the exact scripts slowing your site down, not just say "we'll look into speed." This is the same failure pattern covered in how ghost scripts kill your Shopify speed.
2. Do they target LCP under 1.5 seconds? Largest Contentful Paint is the metric Google uses to judge how fast your site feels to load. A vague promise about "improving performance" is not the same as a stated target.
3. Do they test on iOS Safari specifically? A large share of Shopify traffic checks out on an iPhone. Safari renders checkout pages differently than Chrome, and problems there rarely show up in a standard Google Analytics report.
4. Do they actually work in Liquid? Shopify's templating language is where most rendering problems start. An agency that outsources all development or only touches themes through an app builder cannot fix issues at the code layer.
5. Do they remove app debt? Every app you install adds JavaScript to your store, even after you stop using it. Removing that weight takes technical work, not a design refresh.
How These Rankings Work
Every agency below is a real, established Shopify Plus partner in New York. Several of them do strong work. This is not a list where six agencies get invented flaws so one can look better. The ranking reflects one thing: how much public evidence each agency has that it operates at the technical, code-level layer versus the design and UX layer. Agencies with more public technical evidence rank higher. Agencies whose public case studies are built entirely around visual redesigns and behavioral metrics rank lower, because that is what their own published work shows.
1. Webulux — Conversion Engineering
Webulux is built around a single idea: most Shopify conversion problems are not design problems. They are infrastructure problems. Ghost scripts, slow rendering, layout shift during checkout, and broken behavior on iOS Safari all cost sales in ways a standard GA4 report never surfaces. That is the gap Webulux was built to close, and it is the reason this list exists in the first place.
Instead of running behavioral A/B tests or refreshing visual design, Webulux runs a manual technical audit of the store's code, third-party scripts, and Core Web Vitals, then fixes what it finds. The results are documented with exact numbers, not estimates.
An apparel brand went from a 1.0% to 10.0% conversion rate and $30,000 to $100,000 in monthly revenue in 20 days, after LCP dropped from 4 to 5 seconds down to under 1 second and more than 10 unnecessary apps were removed. A CPG peanut butter brand improved from a 4.3% to 10.1% conversion rate and scaled from $30,000 to $70,000 a month after 847KB of ghost scripts were stripped out, cutting LCP from 5.4 to 1.4 seconds. A health and wellness brand recovered $40,000 a month in 21 days after Cumulative Layout Shift dropped from 0.31 to zero and iOS Safari checkout completion rose from 24% to 39%.
Webulux answers all five framework questions directly: ghost script audits, a sub-1.5-second LCP target, explicit iOS Safari testing, hands-on Liquid development, and documented app removal. Full detail on how this process works is in Shopify Conversion Engineering.
2. We Make Websites
We Make Websites has offices in London and New York and has been a Shopify Plus partner since 2011. Of the agencies on this list, they publish the most public evidence of technical work. Their engineering team maintains a public GitHub with coding standards for Shopify themes, and they built their own compiler, called Basis, to turn custom file structures into Shopify-compatible builds. Their service list explicitly includes performance enhancement and headless and composable commerce, alongside CRO strategy.
What's public: confirmed Liquid development through their open coding guidelines, an explicit performance-enhancement service line, and client work with international brands.
What's not disclosed: no public LCP targets, no stated iOS Safari testing process, and no published numbers on app or script removal. Their case studies, including a mobile-first rebuild for a homeware brand, report user growth metrics rather than rendering or speed data.
3. Roswell NYC
Roswell is a Webby Award-winning Shopify Premier Partner based in New York, working mostly with beauty, fashion, and CPG brands. Their development page stands out on this list because they make a direct technical claim most agencies avoid: they describe themselves as one of the first agencies to launch a Shopify Hydrogen headless storefront, and they explicitly connect page speed to conversion, stating that faster load times after going headless translate into measurable conversion gains.
What's public: confirmed headless Hydrogen experience, use of Shopify Functions and Checkout Extensions, and a stated connection between load speed and conversion rate.
What's not disclosed: no named LCP or Core Web Vitals targets, and no mention of ghost script audits or iOS Safari-specific testing. Their published case studies mostly measure results like ROAS lift and customer lifetime value rather than rendering performance.
4. Mobikasa
Mobikasa is a full-stack e-commerce agency with a New York presence and additional offices across several countries. They work across Shopify, Shopify Plus, and other platforms, combining development with digital marketing services. One detail stands out in their public job listings: they specifically require the ability to "safely remove" third-party Shopify apps, which is a more direct technical signal than most agencies publish.
What's public: confirmed Liquid development, confirmed Shopify 2.0 JSON template experience, and an explicit requirement for safe app removal in their hiring materials.
What's not disclosed: no public LCP or Core Web Vitals targets, no stated iOS Safari testing process, and limited published metrics in their case studies compared to their service claims.
5. Avex Designs
Avex is a Platinum Shopify Plus partner in New York with a strong roster of fashion and lifestyle clients, including reported work with KITH and AriZona Beverages. Their public case studies lead with strong conversion numbers, including a reported 235% conversion increase for a streetwear client following a navigation and UX overhaul.
What's public: confirmed Liquid development through job postings, a Platinum Shopify Plus partner tier, and strong, specific conversion and AOV metrics across multiple named clients.
What's not disclosed: no public mention of Core Web Vitals, LCP targets, ghost script audits, or iOS Safari testing. Every public case study we reviewed attributes results to UX, navigation, and content changes rather than rendering or infrastructure fixes.
6. Barrel
Barrel is a New York-based agency founded in 2006, focused heavily on CPG and food and beverage brands, with reported client work for McCormick and Sweet Loren's. They are a confirmed Shopify Plus agency partner with a distributed team and public job listings that require Liquid and GraphQL experience.
What's public: confirmed Liquid and Shopify API experience, a long operating history, and case studies with specific sales and order metrics for named CPG clients.
What's not disclosed: no public LCP or Core Web Vitals information, no stated iOS Safari testing, and no published detail on ghost script or app debt removal. Their public case studies center on customer journey research and design changes rather than technical performance work.
7. One Rockwell / 1R
One Rockwell is a full-service Shopify Plus agency in New York with a decade of experience and a client list that includes recognizable fashion and beauty names, including a reported 71% conversion rate increase for a beauty brand. Of the seven agencies on this list, their public materials lean the furthest toward design and content, with results attributed to page redesigns, product education content, and user-generated content integration.
What's public: a confirmed Shopify Plus partner tier, more than 100 site launches, and specific, strong conversion results for named clients.
What's not disclosed: we found no public mention of Liquid development specifics, Core Web Vitals, LCP targets, ghost script audits, app removal, or iOS Safari testing anywhere in their published materials. Every case study we reviewed attributes results to design and content rather than the technical layer.
Side-by-Side Comparison
| Agency | Strengths | Gaps (per public materials) |
|---|---|---|
| Webulux | Documented LCP, CLS, and ghost script fixes with exact before/after revenue numbers | Newer case study library than legacy NYC firms |
| We Make Websites | Public GitHub, custom build tooling, headless experience | No published LCP targets or iOS Safari process |
| Roswell NYC | Hydrogen headless experience, speed-to-conversion claim | No stated Core Web Vitals targets or ghost script process |
| Mobikasa | Explicit app-removal requirement in technical hiring | Limited published case study metrics |
| Avex Designs | Strong named-client conversion results | No public performance-layer metrics anywhere found |
| Barrel | Deep CPG client history, confirmed Liquid/API work | No public speed or rendering performance data |
| One Rockwell / 1R | Strong brand-name client roster | No public technical claims found; results tied entirely to design and content |
What This Means for Your Store
None of the agencies above are bad choices. Several have real, verifiable client results. But most of them win by making your store look better, not by finding what is broken underneath it. If your conversion rate is low and your ad spend is high, a new homepage will not fix a checkout that fails on an iPhone or a theme still loading hundreds of kilobytes of scripts from apps you stopped using two years ago. This is the same pattern we break down in why your Shopify conversion rate is low.
Before you hire anyone on this list, including us, ask them the five questions above and see how specific their answers are. That single conversation will tell you more than any portfolio.
If your store is spending $30k+ per month on ads, the agency you need isn't the one with the nicest portfolio. It's the one that finds what's broken in your code. You can book a discovery call for our Shopify Conversion Engineering service, or simply fill out the audit form on our homepage. We will analyze your theme and give you an exact breakdown of what is actually holding your conversion rate down.
Muhammad Usama
Founder & Head Conversion EngineerFounder & Head Conversion Engineer with 8+ years of technical engineering experience. I bridge the gap between full-stack development and e-commerce growth, specializing in tearing down Shopify architectures, eliminating code-level friction, and building high-performance infrastructure for 7- and 8-figure brands.