Every successful ecommerce project starts with a thorough understanding of what you actually need to build. The difference between projects that launch on time and on budget and those that spiral into chaos almost always comes down to how well requirements were documented before development began.
This guide covers the functional requirements every new ecommerce site needs to consider — organized by category so you can build a comprehensive checklist before engaging any development partner or making platform decisions.
Foundation: The Non-Negotiables
Platform and Hosting
Platform selection is a strategic decision, not just a technical one. The right platform depends on your product catalog complexity, B2B vs. D2C model, international requirements, and integration needs. For most mid-market merchants, Shopify Plus offers the best combination of capability, ease of use, and total cost of ownership. For more complex requirements, evaluate BigCommerce or a headless architecture.
Performance
Page speed isn't a nice-to-have — it directly impacts conversion rates and search rankings. Target a Google PageSpeed score above 80 on mobile, with sub-3-second Time to Interactive on 4G connections. This requires discipline from day one: optimized images, minimal render-blocking scripts, efficient Liquid code, and careful app selection.
Security and Compliance
- SSL/HTTPS across the entire domain (not just checkout)
- PCI DSS compliance for payment processing
- ADA/WCAG 2.1 accessibility compliance
- GDPR cookie consent for EU visitors
- CCPA opt-out mechanisms for California residents
User Experience and Design
Homepage
The homepage needs to answer three questions immediately: Who are you? What do you sell? Why should I care? It should establish brand narrative through creative assets, surface your best products and current promotions, and direct visitors toward their likely shopping intent.
Mobile Experience
Over 60% of ecommerce traffic is now mobile — for many demographics and product categories, it exceeds 80%. Mobile design isn't a responsive afterthought; it needs to be the primary design surface. Test checkout completion on mobile specifically — this is where most mobile conversion is lost.
Navigation and Search
For catalogs with more than 100 SKUs, onsite search becomes a critical conversion tool. Consider a dedicated search solution (Searchanise, Boost Commerce, or similar) that supports typo tolerance, synonym handling, and merchandising rules rather than relying on Shopify's basic native search.
Marketing and Analytics Infrastructure
Analytics
- Google Analytics 4 with enhanced ecommerce event tracking (view_item, add_to_cart, begin_checkout, purchase)
- Google Tag Manager for manageable tag deployment
- Server-side tracking for accurate attribution in a cookieless world
Pixels and Tracking
Identify every advertising platform you'll use and ensure proper pixel implementation: Meta (Facebook/Instagram), Google Ads, TikTok, Bing, and any DSPs you work with. These need to fire accurately on the right events — particularly the purchase event — for your ad platforms to optimize effectively.
Email Marketing
- Choose your ESP before launch: Klaviyo (most common for Shopify), Listrak, or Mailchimp
- Set up transactional flows at launch minimum: order confirmation, shipping notification, delivery confirmation
- Configure abandoned cart recovery before your first visitor arrives
- Build a welcome series for new email subscribers
Operations: Shipping and Payments
Shipping Configuration
- Document all your shipping zones, carriers, and rate structures
- Decide between flat rate, calculated (real-time carrier rates), or free shipping thresholds
- Configure shipping for international markets if applicable
- Address dimensional weight pricing if you ship large items
Payment Methods
Offer more than credit cards. The standard modern ecommerce payment stack includes:
- Credit/debit cards via Shopify Payments or a payment gateway
- PayPal (still used by a significant buyer segment)
- Apple Pay and Google Pay (one-tap checkout significantly improves mobile conversion)
- Buy Now Pay Later: Klarna, Afterpay, or Affirm (especially important for higher AOV products)
Advanced Features to Plan For
Not every store needs these at launch, but knowing which you'll eventually need helps you choose the right platform and architecture from day one:
- International selling: Multi-currency, multi-language, international shipping, localized content
- Product reviews: Embedded reviews build conversion trust significantly — plan for a review platform from launch
- Loyalty program: Repeat purchase rates improve substantially with structured loyalty mechanics
- Returns management: Self-service returns reduce customer service volume and improve customer satisfaction
- B2B capabilities: If you have any wholesale customers, plan for this before platform selection — retrofitting B2B on a D2C architecture is painful
- Store locator: Required for any brand with physical retail presence
- Subscription products: If any products are candidates for subscription models, evaluate platforms and apps before launch
Backend Integrations
The systems that need to connect to your ecommerce platform determine your integration architecture:
- ERP: Products, pricing, inventory, and order data needs to flow bidirectionally. This is the most complex integration for most merchants — budget accordingly.
- 3PL / Warehouse Management: If you use a third-party fulfillment provider, orders need to route there and tracking needs to come back.
- Shipping software: ShipStation, EasyPost, or Shippo for rate shopping and label generation if you ship in-house.
- Tax engine: Avalara or Vertex for merchants with complex multi-state tax obligations.
The Requirements Document
Pull all of the above into a structured requirements document before engaging any development partner. A detailed requirements document lets you:
- Get accurate quotes (not ballpark estimates that balloon)
- Evaluate platforms against your actual needs
- Identify integration complexity early
- Set realistic timelines
- Reduce mid-project scope changes
Merchants who invest in thorough requirements documentation before development begins consistently have better outcomes — shorter timelines, fewer surprises, and lower total project costs — than those who figure it out as they go.