Migrating an e-commerce platform is a high-stakes project. Your old store needs to stay live while the new one is being built. Products, customer accounts, order history, and SEO rankings all need to survive the transition. A missed redirect or a broken checkout flow on launch day costs real revenue.

Most e-commerce migrations that go wrong weren't technically difficult—they were poorly sequenced. SEO work started after launch instead of before. Payment integration was tested a day before cutover. Product data was migrated once but never validated for completeness. A Gantt chart enforces the right sequence and makes every dependency visible before it becomes a crisis.

Prerequisites

Lock these down before building your timeline:

Target platform confirmed. Shopify, BigCommerce, WooCommerce, Magento 2, custom? The platform determines your migration approach, tool availability, and technical complexity.
Scope defined. Products, categories, customer accounts, order history, blog posts, custom pages—what migrates and what gets left behind?
SEO baseline documented. Export your current page URLs, ranking keywords, and backlink profile before any migration work starts. You need this to build your redirect map.
Current platform access for export. Confirm you can export all necessary data from the old platform in usable formats. Some legacy platforms make this difficult.

Phase Breakdown

Phase	Key Tasks	Duration	Dependencies	Owner
Discovery & Planning	Scope doc, URL inventory, SEO audit, data export assessment	1–2 weeks	Stakeholder sign-off	PM + Developer
Platform Setup	New platform provisioning, domain config (staging), basic settings	1 week	Platform selected and contract signed	Developer
Theme Development	Select or build theme, configure navigation, mobile optimization	2–4 weeks	Platform setup complete	Frontend developer
Product Data Migration	Export from old platform, clean and transform, import to new platform	1–3 weeks	Data export confirmed	Developer
SEO Redirect Map	Map all old URLs to new URLs, configure 301 redirects	1–2 weeks	Product migration complete	SEO + Developer
Payment & Shipping Integration	Configure payment gateway, shipping zones, tax settings	1 week	Platform setup complete	Developer
App & Integration Setup	Third-party apps (email marketing, loyalty, reviews, analytics)	1–2 weeks	Platform setup complete	Developer
QA & Staging Testing	Full store review, checkout flow, mobile, page speed, broken links	1–2 weeks	All setup complete	QA
Cutover	DNS switch, redirect activation, post-launch monitoring	1–2 days	QA passed	Developer
Post-Launch	Search console resubmit, crawl error monitoring, performance review	1 week	Cutover complete	SEO + Developer

Step-by-Step Gantt Construction

Step 1: Add product data migration before theme development completion

Product migration and theme development can run in parallel—you don't need a finished theme to migrate product data. Start product migration once the platform is set up, not after the theme is complete. This saves one to two weeks on the critical path.

Step 2: Make the SEO redirect map a tracked deliverable

The redirect map—a spreadsheet mapping every old URL to a new URL—is the most important pre-launch deliverable for SEO. Add it as a distinct row with an explicit owner and a completion date before the cutover row can start. Redirect maps discovered to be incomplete the day before launch are one of the most common e-commerce migration failures.

Step 3: Add payment integration as a parallel track

Payment and shipping configuration doesn't depend on the theme or product migration—it depends only on the platform being set up. Start it in week two, not week six. Parallel payment integration means any merchant account or configuration issues are discovered early rather than the week before launch.

Step 4: Schedule QA with a full two weeks

One week of QA for an e-commerce migration is not enough. Add two full weeks: week one for developer QA (broken links, missing images, redirect verification, checkout flow), week two for stakeholder review (the business owner clicks through every key page and tests the checkout with a real order). Build a named QA checklist as a required deliverable.

Step 5: Plan the cutover as a time-boxed event, not an open-ended task

The cutover row should have a start time, not just a start date. DNS propagation takes up to 48 hours. Plan the cutover for a Tuesday or Wednesday morning when traffic is low, your team is available, and you have two full days to monitor before the weekend. Use gantt-chart.io to add a time-specific milestone on the cutover row.

Common Mistakes

Migrating products once and not re-validating before launch. Products change between migration and launch. Add a "product audit" task in the final QA week to confirm product counts, variants, images, and prices against the old platform.

No 301 redirect for every changed URL. Missing redirects lose both traffic and link equity. Your redirect map should account for every product, category, blog post, and custom page URL that's changing. Validate it with a redirect checker tool before the DNS switch.

Ignoring page speed on the new platform. A theme that looks great but loads in four seconds will hurt both conversions and SEO. Add page speed testing (Core Web Vitals) as a specific QA task with pass/fail criteria.

Not resubmitting sitemaps after launch. After cutover, submit the new sitemap to Google Search Console and request recrawl of the key pages. Add this as a task on day two post-launch.

Forgetting customer account data. If customer accounts are migrated, test the account login flow. If passwords need to be reset (common when migrating platforms), set up the reset email flow before cutover.

Template Example

A 12-week e-commerce migration from Magento to Shopify:

Weeks 1–2:   Discovery, URL inventory, SEO audit, data export assessment
Week 2:      Platform setup (Shopify provisioning, staging domain)
Weeks 2–5:   Theme development (selection → customization → mobile QA)
Weeks 2–4:   Product data migration (export → clean → import)
Weeks 2–3:   Payment & shipping configuration (parallel)
Weeks 3–5:   App integrations (email, reviews, analytics)
Weeks 4–5:   SEO redirect map (maps old URLs to new)
Weeks 6–7:   Full QA (developer QA + stakeholder review + checkout test)
Week 7:      Product audit, redirect validation, page speed audit
Week 8:      Buffer + final fixes
Tuesday week 9: Cutover (DNS switch + redirect activation)
Week 9 post: Search console resubmit, crawl error monitoring

Next Steps

Before you start development, get a complete URL export from your current platform and verify your product export format is compatible with the new platform's import tool. These two technical confirmations can either save weeks or add them—knowing early is the only way to adjust. Share the Gantt chart with your developer, SEO lead, and business owner, and walk through the cutover plan together before committing to a launch date.