Creating an online store isn't just about theme or aesthetics. It's a business project that involves your offering, your positioning, your acquisition strategy, your operations, and your profit margin. In this guide, I'll show you how to evaluate an online store creation agency using objective criteria, how to structure your project to avoid pitfalls, and what a serious process looks like—from the initial audit to post-launch iterations. The goal: to choose a partner that delivers a store that ranks well, converts well, and scales effectively.
Why use an online store creation agency?
A good agency reduces risk and accelerates time-to-market. It brings to the table dozens of comparable projects, proven design patterns, component libraries, and a governance structure that avoids costly back-and-forth. Where a handcrafted approach would "reinvent the wheel," an agency industrializes: designing the customer journey, managing variants, pricing rules, logistics, technical SEO, performance, and tracking.
This is essential when your project goes beyond a simple online storefront: medium to large catalogs, integration constraints (ERP, CRM, WMS, PIM, advanced payment systems, invoicing), multi-country tax regulations, internationalization, B2B markets, subscriptions or bundles, or when your brand aims for a premium UX/UI experience. In these contexts, mistakes result in hidden costs (maintenance, technical debt), lost search engine rankings, or missed conversions.
Conversely, if your specifications are minimal, an experienced freelancer or an in-house team may suffice. But the question isn't simply "who costs the least." It's primarily: who possesses the methodology, the evidence, and the ecosystem to deliver quantifiable results on your KPIs?
If you want to create your online store with Shopify, you can check out our article on the best Shopify agencies in France .
Define your e-commerce project before consulting an agency
Before requesting quotes, clarify your business model and objectives. A high-performing agency will challenge you on these points. What are your revenue, margin, average order value, purchase frequency, and customer acquisition cost targets? What role should the website play in your marketing mix (direct sales, physical stores, drive-to-store)? Without these benchmarks, you're comparing quotes based on appearances—not on their ability to deliver results.
Describe your offer and your catalog: brand positioning, the sector in which you operate, then more specifically the structure of the collections, your products, the future filtering logic… Also anticipate the content: blog and articles, guides, comparison tools, social proof, media…
Finally, map the technical constraints: existing systems (ERP, CRM, WMS, PIM), shipping and return methods, marketplaces, accounting and tax requirements, and compliance (GDPR, consent management, payment methods). This inventory will determine the appropriate platform, connectors, integration effort, and risks to mitigate.
Once you have all these elements, you put them all together in a specifications document to send to the agencies.
Criteria for choosing an online store creation agency
Evaluate an agency based on evidence and methodology, not on rhetoric.
A thorough knowledge of the e-commerce platform
Your target platform—Shopify, WooCommerce, PrestaShop, or another—should be familiar territory, with use cases comparable to yours (catalog size, variant logic, countries/languages, B2B, subscriptions, etc.). Ask for concrete demonstrations and real performance metrics, not promises.
It's important to understand that each platform has its own strengths. Shopify shines thanks to its ecosystem, robust checkout, robust security and maintenance support, and the emergence of modern tools for international expansion, subscriptions, bundles, and a vast app store. WooCommerce and PrestaShop offer different paths, particularly for those seeking granular control over server-side code or specific use cases.
The choice is not dogmatic. It depends on your catalog, your integration constraints, your international ambitions, and your internal capacity to maintain it.
Technical expertise to create an e-commerce platform that transforms
A successful website relies on a well-crafted, readable codebase designed for real-world performance. This is precisely what you should verify with an agency. Ask to see how their teams mark up HTML semantically—each element should have a clear purpose for browsers, screen readers, and search engines. Observe their CSS approach: a simple architecture, reusable styles, and a variable system that avoids rule stacking, conflicts, and massive stylesheets. On the JavaScript side, look for intelligent restraint: interactions added only when necessary to maintain rendering speed and visual stability. On Shopify, demand structured Liquid templates, well-defined blocks, and factored logic to minimize duplication and unnecessary queries. An agency that masters these fundamentals can demonstrate this by sharing its templates and explaining its conventions.
Finally, the technical requirement isn't about multiplying costly developments, but about aiming for efficiency. A reliable agency prioritizes essential usefulness, refactors its components, documents its choices, versions its code, and conducts systematic reviews. It justifies every line of code by its impact on product understanding, maintainability, and business performance. This pragmatism—ambitious simplicity, backed by evidence—should guide your selection: it's what distinguishes a merely attractive agency from one that transforms.
An e-commerce strategy that increases revenue
A high-performing online store doesn't "endure" conversion; it actively shapes it. E-commerce strategy aligns three key levers—optimizing conversion rates, increasing average order value, and boosting purchase frequency—around a single principle: every touchpoint must help users decide faster and return more often, without forcing or obscuring the perceived value. When choosing an agency, look for one that transforms this principle into a measurable management framework, not just a collection of "tips and tricks."
CRO is first and foremost a methodology. A good agency formalizes hypotheses based on data (customer journeys, internal research, heatmaps, verbatim comments), translates them into testable variations (information order, evidence in the right place, less friction, more reassurance), and then measures the effect on clear objectives: add to cart, progress through checkout, conversion rate, margin. It knows how to explain why a change in hierarchy on the product page, a better presentation of variants, or a clearer mini-cart can have a real impact on your sales.
A competent agency develops merchandising guidelines (which products to offer, when, and based on which signals), tests the presentation (more readable cards, clear options, fair comparisons), and monitors the actual impact: AOV, margin per order, and customer loyalty. It warns you against constant promotions that devalue the brand and prioritizes value (quality, usability, evidence) rather than simply reducing prices.
Purchase frequency is earned after the order as much as before. Retention journeys aren't just about a newsletter: they encompass post-purchase activities, reordering, usage content, reviews, referrals, loyalty programs, and subscriptions when relevant. The agency you select should be able to discuss cohorts (returns at 30/60/90 days), segments (first purchase vs. loyal customers, distinct categories), and timing (before a consumable product runs out, seasonality, usage cycles). It should link its actions to a central metric: customer lifetime value and its ratio to acquisition costs. Again, ask for concrete workflows, key messages, and observed results.
If you want to learn more about e-commerce strategy, here is an article on how to boost the conversion of your online store .
A UX design that guides the purchase
Good user experience design isn't about "looking pretty"; it's about organizing attention to guide users seamlessly from need to purchase. The work begins upstream with understanding user behavior: what problems does the user want to solve, what objections are hindering their decision, and what information tips the scales? A reputable agency translates these answers into clear user journeys, where each screen has a specific role and each interface element has a measurable purpose.
Visual hierarchy is the foundation. Informative titles, subtitles that frame the promise, useful (not decorative) images, explicit labels, and visible and consistent calls to action: all contribute to reducing cognitive effort. On a product page, this is immediately apparent: clear variations and sizes, legible prices and benefits, evidence (reviews, real photos, warranties) in the right place, and shipping and returns explained before the final click.
The design must be both mobile-first and accessible. Native gestures, touch targets, contrasts, tab order, error messages – all of this is anticipated and tested.
Micro-copywriting (the words used in the interface) is just as important as the overall design. Precise labels, concrete reassurance messages, and error messages that explain what to do next: this is often where a conversion point is gained.
SEO that helps you gain rankings
On-page SEO is judged by the templates, not by piecemeal tweaks. Ask how the agency models heading tags, Hn headings, snippets, and the order of information on list and fact sheets pages. A good answer will mention structured fields, controlled generation rules, properly handled exceptions, and a component system that avoids duplication. Regarding structured data, expect to see a clear schema (Product, Breadcrumb, FAQ, Organization) designed for your templates, tested, and monitored.
On the technical side , the agency must show how it avoids the classic pitfalls that weigh down visibility: poorly managed URL parameters, worthless indexed facets, duplicate content between variants, poorly implemented pagination, absence of relevant canonicals.
Performance isn't just an aesthetic option; it's a revenue driver—and a deciding factor. Ask the agency about its asset strategy: images served at the correct dimensions, a clear distinction between critical and non-essential resources, non-vital scripts loaded later, and limited, audited external dependencies. Request concrete examples where removing a carousel, replacing a library, or streamlining animation improved speed and conversion. A good agency will talk about fast first renders, stable content, and progressive enhancements; it will be able to demonstrate real before-and-after metrics, not just a lab score.
If you're migrating or redesigning your site, SEO recovery is a crucial test. A reliable agency will perform a URL inventory, map the new pages, implement careful redirects, transfer metadata and schema markup, conduct post-launch checks, and put safeguards in place to address any issues. They will also detail the Search Console setup, monitor crawl errors, and develop a rapid response plan for the initial weeks.
Support that secures the project
Success depends not only on what is delivered, but also on how it is delivered and then maintained. A good agency manages the project with simple and effective rituals: regular check-ins, a prioritized and visible backlog, explicit acceptance criteria, and a clear escalation process in case of roadblocks. During production, you need to know the status of the mockups, what risks exist, and how they will be addressed. This governance reduces unforeseen events and protects both your deadlines and your budget.
Another hallmark of serious support is post-launch assistance. The first thirty days are crucial: rapid fixes, close monitoring of metrics (traffic, actual speed, errors, conversion), verification of redirects and tracking, and micro-UX adjustments where real-world conditions demand it. A mature agency anticipates this phase, with dedicated staff, clearly defined response times, and a concrete communication plan.
Your autonomy is part of the support we provide. Demand documentation of the templates, data layer mapping, access to tools, and a planned skills transfer: training for your team, contribution guides, deployment checklists, and rollback procedures. An agency that wants you to succeed will gradually empower you to manage day-to-day operations independently.
Examples of online stores
Evaluating an agency's portfolio is a crucial step in the selection process. A well-rounded portfolio provides a concrete overview of the agency's creative and technical capabilities. Assess not only the aesthetics of the websites but also their functionality. Try browsing a few of the listed sites to see how intuitive they are, both on mobile and desktop. Check the loading speed, SEO, and overall user experience.
Don't hesitate to ask the agency for detailed case studies or specific examples of projects similar to yours. This will allow you to better understand their approach and the results they've achieved for other clients in comparable situations. A transparent agency that takes pride in its work will always be willing to share this information to demonstrate its competence.
The importance of customer reviews and testimonials
Customer reviews and testimonials are invaluable sources of information when selecting an agency. They offer a direct perspective on the experiences of other companies that have worked with the agency in question. Check reviews on reliable platforms like Sortlist or Malt. Testimonials on the agency's website can also be informative, although they are often selected to highlight the most positive aspects.
It's important to consider both positive and negative reviews. Positive reviews will give you an idea of the agency's strengths, such as their technical expertise, creativity, or customer service. Negative reviews, on the other hand, can alert you to potential problems such as delays, poor communication, or budget overruns. Pay attention to how the agency responds to negative feedback, as this can reveal a lot about their professionalism and commitment to customer satisfaction.
To delve deeper, try contacting some of the agency's previous clients directly. Ask them specific questions about their experience, the challenges they faced, and how the agency helped them overcome them. A satisfied client will generally be willing to share their experience in detail, giving you a more complete and honest picture of what you can expect when working with the agency.
What a serious online store creation offer should include (and how to evaluate it)
A good proposal isn't a quote with three lines and a price. It's a framework that describes what the agency will deliver, how, the associated risks, the acceptance criteria, and the success plan after launch. It should read like a project manual, precise enough to avoid any blind spots, yet pragmatic enough to remain achievable.
The document begins with a clear framework: business objectives, priorities (what absolutely must be ready at launch and what can come later), target audiences, known technical constraints, assumptions, and risks. A credible proposal restates your needs and challenges them tactfully; if everything is accepted without discussion, be wary. Next come the deliverables for each phase: workshops and e-commerce strategy, mockups and design system, development and integrations, content production/import, on-page SEO integrated into templates, tagging plan and data layer, testing, potential migration plan, go-live, and ongoing maintenance/support.
How much does it cost to create an online store?
Budget is a key factor when choosing an agency to create your online store. Understanding the various costs associated with this type of project is essential to avoid surprises and plan your finances effectively. Budgets can vary significantly from one agency to another, depending on their reputation and the specific requirements of your project. Therefore, it's important to request detailed quotes from several agencies to compare their offers.
The costs of creating an online store typically include website design and development, payment system integration, e-commerce functionality setup, and potentially additional services such as SEO, digital marketing, or product photography. Some costs may be one-time expenses, while others, like maintenance and support, may be recurring. Be sure to clarify these aspects with the agency to avoid misunderstandings.
It's also crucial to consider the return on investment (ROI) of your online store. An agency that can offer a high-quality, well-optimized solution can generate more sales and revenue, thus justifying a higher initial cost. Don't forget to also factor in the time and effort you'll save by working with professionals. Ultimately, the cost should be weighed against the added value the agency brings to your project.
Here are some figures to give you a general idea. A "starter" project (limited catalog, few integrations, semi-custom design) can be priced at the lower end, between €4,000 and €8,000. A brand website with an advanced design and extensive integrations (logistics, multi-country, ERP, PIM, B2B with complex pricing rules) naturally increases in price. Some sites can easily reach tens of thousands of euros, depending on the agency you choose.
A good quote clearly outlines these factors and links billing milestones to clear deliverables, with a realistic timeline. Consider the total cost of ownership: licenses, applications, maintenance, upgrades, content production, and internal time. The agency can help by detailing the cost of each item.
Common mistakes to avoid when creating an online store
Most projects that go off track don't do so because of a "bad idea," but because of known blind spots that could have been prevented. Avoiding them starts the moment you choose the agency: what you are shown (or not shown), how risks are framed, and the precision of deliverables and acceptance criteria are far more reliable indicators than any promise.
First mistake: underestimating content production. A perfect architecture is useless if the product pages are sparse, the visuals generic, and the social proof lacking. A reputable agency integrates content into the planning, quantifies the editorial effort, defines roles (who writes, who approves, who integrates), and provides ready-to-use templates. If the offer postpones "content" until later, you'll pay the price in SEO and conversions.
Second mistake: ignoring SEO recovery during a redesign or migration. Without a URL inventory, precise mapping, tested 301 redirects, and metadata and schema transfers, you'll inevitably lose traffic. Ask for an example of a previously executed migration plan, the post-switchover checks performed, and before/after metrics. An agency that addresses this at the end of the project enhances your online visibility.
Third mistake: piling on features and apps without governance. Each dependency bloats the front end, multiplies points of failure, and complicates maintenance. The right approach is to start with real needs, favor native components, and document each addition (cost, impact, rollback plan). Beware of "just in case" option catalogs: efficiency always trumps excess.
Fourth mistake: neglecting measurement and quality. A website without a proper tagging plan, a reliable data layer, QA rituals, and performance thresholds is essentially flying blind. The agency must present its test plan, target thresholds (speed, accessibility, stability), pre-launch checklist, and hypercare system. Otherwise, bugs and technical debt will inevitably creep into the production environment.
Fifth mistake: confusing design with clarity of navigation. Aesthetically flawless pages can fail if the information hierarchy is unclear, calls to action are weak, or variations are incomprehensible. Ask for navigable prototypes (not just mockups), a living design system, and, above all, examples where a design decision has yielded a measurable benefit.
Finally, believing that a launch marks the end of the project is a costly mistake. The first thirty days are for stabilizing, measuring, and correcting; the following months are for optimizing. Verify that the offering includes hypercare, then application maintenance (TMA), and a roadmap of CRO/SEO iterations. Without this framework, performance slowly erodes… until the next overhaul.
Agency vs. freelance: which to choose depending on your situation?
If your project is simple, a senior freelancer can deliver quickly and efficiently. However, as soon as the complexity increases—integrations, international expansion, high-stakes SEO, system design, or stringent performance requirements—an agency provides bandwidth, specialization, and guaranteed continuity. To learn more, please refer to our article on Shopify freelancers vs. Shopify agencies .
What are the timeframes for designing and launching an online store? (and how to estimate them with an agency)
Deadlines aren't just a matter of "speed of execution"; they reflect the quality of the project scope, the availability of your content, the number of technical integrations, and the rigor of the testing process. A reliable agency provides a timeline that links each step to measurable deliverables and expected client decisions. Otherwise, weeks slip by because decisions are delayed, content doesn't arrive, or testing starts too late.
In a standard scenario, four key phases are observed. The scoping phase (one to three weeks) clarifies objectives, scope, information architecture, and risks; it establishes the acceptance criteria for each batch. The user experience and interface phase (two to four weeks, depending on the number of templates) produces wireframes, clickable prototypes, and a design system; iterations are limited from the initial proposal stage. The development and integration phase (three to eight weeks) transforms these choices into live pages: themes, configurable blocks, payment connections, logistics, potential ERP or CRM integrations, and product and media import. Finally, the quality assurance and deployment phase (two to three weeks) covers functional testing, accessibility, real-world performance, structured data, migration plan and redirects if a redesign is required, followed by a managed switchover and intensive stabilization support over thirty days.
These timeframes lengthen or shorten depending on three key factors: content preparation (product sheets, visuals, social proof, brand pages), the complexity of integrations (shipping, warehousing, accounting, subscription management, tiered pricing in B2B), and internationalization (languages, currencies, taxes, market pages). The best way to meet the deadline is to finalize the architecture early, deliver content in prioritized batches, and quickly resolve interface issues (variants, filters, reassurance messages) to prevent a snowball effect.
In practical terms, expect these realistic orders of magnitude, within a controlled scope:
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“Starter” launch (limited catalogue, few integrations, semi-custom design): 6 to 8 weeks until go-live.
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Brand store (medium catalog, custom design, advanced logistics and payment connectors): 10 to 14 weeks, including content migration and SEO by design plan.
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Complex project (ERP/CRM integrations, B2B pricing rules, multiple countries, high-stakes SEO overhaul): 16 to 24 weeks with intermediate milestones and batch switches if necessary.
