Migrating your CRM or email service provider is one of the most impactful decisions a B2C brand can make. Whether you’re moving from Mailchimp or another legacy platform, the transition to Klaviyo represents more than a tool change. It’s a shift in how you manage customer data, personalisation, and lifecycle marketing.
Klaviyo was built specifically for B2C brands, offering deep integrations with e-commerce platforms, advanced segmentation, predictive analytics, and native SMS capabilities. But success depends on timing, planning, and execution.
Drawing on insights from experienced migration leaders across top agencies, this guide answers the most important questions brands ask when considering a move to Klaviyo: covering timelines, technical challenges, data migration, list hygiene, and post-launch optimisation.
Why Do Brands Migrate To Klaviyo?
Many brands outgrow their existing ESP as their data, channels, and personalisation needs become more complex. Common reasons for switching include:
- Limited segmentation and automation flexibility
- Difficulty unifying email, SMS, and customer data
- High technical overhead for marketers
- Inflexible integrations with e-commerce platforms
- Poor visibility into lifecycle and revenue attribution
Klaviyo addresses these challenges by combining a customer data platform with powerful email and SMS tools, allowing marketing teams to move faster without heavy engineering support.
How Long Does A Full Klaviyo Migration Take?
There is no universal timeline, but experienced partners generally recommend a minimum of one month for a well-executed migration.
Typical planning ranges look like this:
- Under 50,000 subscribers: ~4 weeks
- 50,000–250,000 subscribers: 5–6 weeks
- 250,000+ subscribers: 6–8 weeks
Larger lists require more time for data validation, segmentation rebuilds, and deliverability ramp-up.
“No two migrations are the same. The scope, list quality, and technical complexity all play a role.”
What If You’re Starting Late?
If time is limited, brands can still succeed by narrowing focus:
- Work with an experienced Klaviyo partner
- Prioritise revenue-critical flows only
- Defer advanced automations and redesigns
- Keep your legacy ESP active as a temporary fallback
- Plan post-migration optimisation instead of perfection
A strong partner dramatically reduces risk and accelerates execution.
How To Prioritise What Matters Most
The “core to enhanced” migration strategy
When timelines are tight, experts recommend a core-first approach:
Must-have on day one
- Sign-up forms
- Welcome series
- Abandoned cart flows
- Core segments (engaged, purchasers, VIPs)
- Transactional emails
Can follow later
- Advanced lifecycle flows
- Complex personalisation logic
- Template redesigns
- Lesser-used segments
This ensures you’re functional and revenue-ready before layering on sophistication.
Migrating Email vs. SMS: What’s Different?
Email migration requires warming, testing, and careful sequencing. SMS, on the other hand, is more immediate.
Key differences:
- Email needs deliverability ramp-up
- SMS can reach your full opted-in list right away
- SMS flows are faster to implement but must follow strict compliance rules
Essential SMS flows to have live early
- SMS welcome series
- Abandoned cart reminder
- Browse abandonment
- Post-purchase thank you
- Back-in-stock alerts
- Price drop notifications
Red Flags: When To Delay Migration
A migration won’t fix foundational problems. Experts recommend pausing if you see multiple warning signs:
- Understaffed or unowned email programs
- No internal lifecycle owner
- Poor list hygiene or inflated databases
- Weak attribution or tracking
- Unstable or overly complex tech stacks
Before migrating, conduct a deep audit and define your data needs for the next 12–36 months. Clarity now prevents rework later.
Technical Considerations and QA
Common technical hurdles
- Broken or unmapped sign-up forms
- Missing custom properties
- Overwritten data from dual ESP connections
- Complex third-party integrations
Rigorous QA is essential.
“QA is where migrations fall apart. Every flow, link, and personalisation token must be tested in a real inbox.”
Best Practices For Technical Validation
- Test every form submission path
- Validate flow triggers and delays
- Preview emails on mobile and desktop
- Send real test emails—not just previews
- Use parallel environments where possible
Migrating Automations The Right Way
A migration is an opportunity to reset, not replicate mistakes.
Before rebuilding flows, ask:
- What’s working today?
- What’s broken or over-engineered?
- What outcomes actually matter?
Rather than copying legacy logic, teams should map intent and rebuild flows using Klaviyo’s native capabilities, cleaner conditions, and smarter segmentation.
Data Preservation: What Moves & What Resets
Will you lose subscriber data or history?
No. Subscriber profiles, properties, tags, and engagement data can be migrated. However:
- Historical opens and clicks may not fully carry over
- Segment logic often needs to be rebuilt
- Predictive analytics quickly fill performance gaps
Manual segment rebuilding is often preferred. It ensures accuracy and relevance in the new system.
List Hygiene: Non-Negotiable Before Migration
Cleaning your list before import protects deliverability and performance.
Essential list-cleaning steps
1. Remove inactive subscribers
- Suppress users unengaged for 12+ months
2. Import suppression lists
- Hard and soft bounces
- Unsubscribes
- Spam complaints
- Global suppressions
3. Eliminate low-quality contacts
- Contest and giveaway entries
- Purchased lists
- Role-based emails
- Fake or malformed addresses
4. Validate formatting
- Missing symbols
- Invalid domains
- Extra spaces or characters
5. Identify your best contacts
- Recent openers and clickers
- Recent purchasers
- High-value customers
A smaller, healthier list consistently outperforms a bloated one.
Template And Creative Migration
Rebuild. Don’t copy.
Simply pasting old templates limits Klaviyo’s power. Rebuilding inside Klaviyo allows you to leverage:
- Native dynamic blocks
- Better mobile responsiveness
- Accessibility improvements
- Faster iteration and testing
Dynamic personalisation should be recreated using Klaviyo’s variables and templating language, carefully mapping old merge tags to new properties.
Cost, ROI, and Learning Curve
What about pricing?
While pricing models differ, many brands find savings in:
- Reduced technical overhead
- Faster campaign execution
- Less reliance on engineering
Is Klaviyo hard to learn?
Most teams report:
- Fast onboarding for basic use
- Moderate learning curve for advanced flows and analytics
- Strong self-serve resources via Klaviyo Academy
Post-Migration Testing And Monitoring
What to test before going live
- Form behaviour
- Flow triggers and logic
- Segment accuracy
- Rendering across inboxes
- Deliverability via seed lists
After launch, monitor closely
- Flow revenue
- Send and bounce rates
- Unsubscribes
- Error logs
- Engagement trends
Proactive monitoring in the first two weeks prevents small issues from becoming major problems.
Measuring Migration Success
Successful migrations share common outcomes:
- No interruption to lifecycle messaging
- Improved automated revenue
- Better deliverability and engagement
- More flexible segmentation
- Faster campaign execution
Ultimately, success is measured by performance. Not just completion.
Lessons From The Field
The most damaging mistakes are avoidable:
- Skipping domain warming
- Forgetting suppression lists
- Rushing QA
- Copying broken legacy logic
The most successful migrations start early, involve clear ownership, rely on expert partners, and treat migration as a strategic reset—not a lift-and-shift.
Ready to migrate?
Moving from Mailchimp to Klaviyo can be a turning point for your marketing program. With the right preparation, partners, and priorities, the transition becomes an opportunity to simplify operations, unlock better data, and build a stronger foundation for growth.
Start early. Clean your data. Test everything. And don’t bring old problems into a new platform.
Klaviyo is built for B2C brands. Make sure your migration strategy is too.
Need a fresh perspective? Let’s talk.
At 360 OM, we specialise in helping businesses take their marketing efforts to the next level. Our team stays on top of industry trends, uses data-informed decisions to maximise your ROI, and provides full transparency through comprehensive reports.
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