Code Migration Website Design & Development

Moving Forward Without Breaking What Works

Code migration is the process of moving an application, codebase, or website from one environment to another—whether that means upgrading a legacy CMS, switching to a modern framework, replatforming to a new cloud provider, or even just translating a codebase from one language to another . In practice, migration projects are about trading one set of constraints for another: moving from a platform you have outgrown to one that offers better performance, maintainability, and scalability .

The challenge is that migrations are notoriously risky. Teams often find themselves caught between client budgets and the need for thorough modernization. When the client is "happy" with the look and feel but the underlying technology—jQuery, inline scripts, old Node versions—is a security and maintainability risk, you have to decide: keep it as-is or renovate ? The best approach is often a gradual one, moving piece by piece while validating that nothing breaks along the way .

Why Code Migration Is Different

Code migration is fundamentally different from greenfield development. You are not building from scratch—you are replacing the engine of a moving car while keeping the passengers comfortable and unaware .

The Moving Target Problem: Legacy systems accumulate layers of content and structural debt over time. As one team described it, working on a large legacy project feels like untangling Christmas lights—you try to fix one thing, and another breaks . The chance to migrate such a project to a new stack is a welcome one, but it requires a pragmatic, focused approach.

The "Happy Client" Paradox: Clients are often attached to the visual design and user experience of their existing site, even when the underlying technology is outdated . This creates tension: the client wants stability, while the technical team knows the codebase is a ticking time bomb.

The Platform Dependency Trap: Choosing a low-code or hosted CMS solution can be exactly what a team needs at the time—easy for non-technical users, quick to launch . But over time, that convenience becomes a constraint. One team documented how they became highly dependent on their platform, with their entire content library hosted on infrastructure they had very little flexibility to move out of .

Key Approaches to Code Migration

The Strangler Fig Pattern

The Strangler Fig pattern is a gradual migration strategy where you incrementally replace parts of a legacy application with new services, routing traffic to the new system over time . This approach minimizes risk by keeping the old system running while the new one is built and tested.

In Practice: Dutch property platform funda rebuilt their legacy Listing Detail page using Vue and Nuxt3. Their approach was to have the new page running in production on a different URL, gradually moving traffic to it . When they were confident the new page was stable, they simply flipped the switch .

Key Advantage: The gradual rollout allowed them to "fine-tune the new page gradually, minimizing the risk of disruption" . Users experienced no downtime or noticeable change in functionality.

The Shadow Team Model

Migration projects often benefit from a small, dedicated team working independently outside the regular workflow . This approach enables agility—with only a few hands on deck, team members have clear responsibilities and can power through tasks without lengthy approval processes.

Key Practices:

• Unblocked Mindset: If a certain aspect of a task couldn't be finished, the team still finished the rest and revisited it later. The goal was to never be blocked by something they couldn't directly fix themselves .
• Production from Day One: Going live with essentially an empty page (hidden) allowed the team to get a clear understanding of core performance and resource management before components were built .
• Focused Meetings: Fewer, shorter meetings meant more time on actual development .

The Atomic Migration Strategy

Atomic Design, created by Brad Frost, is a system for working with the fundamental building blocks—the atoms—of modern web interfaces . Applying this to migration means breaking your application into basic components and stitching them together in a low-risk, nondisruptive way .

The Approach: Determine if your existing application requires a rewrite, explore how Atomic Design breaks up complex interfaces into discrete pieces you can focus on one at a time, and learn when to perform a synchronous versus asynchronous migration .

Code-First Migration

One team made the jump from a hosted CMS (Webflow) to a code-first setup using Claude Code. They pulled the whole website and its content library, parsed it with AI, created a skeleton using an open-source headless CMS, and migrated all content to Markdown .

The Result: Two hours later, a functional, viable draft containing the entire content of the old website was online. It took a few more hours to set up proper redirects, SEO, and debugging .

Unexpected Benefit: The shift forced less technical team members to engage with version control, IDEs, and CLIs, lowering the "understanding gap" between teams .

AI-Assisted Code Migration

AI is reshaping code migration. Tools like Anima can turn any website into clean, responsive React or HTML code by analyzing the layout, design, colors, and structure . This is not a static "save as HTML" tool—it generates semantic, customizable, production-ready code .

How It Works:

• Paste a website URL into Anima
• The tool extracts layout, design, colors, and structure
• It generates responsive, editable frontend code 

Limitations to Be Aware Of: Dynamic content loaded via JavaScript may not clone completely; login-protected pages require the Chrome extension; complex animations aren't captured .

For enterprise-scale migrations, specialized platforms like Second provide AI agents for codebase migrations, including proprietary codebase scanners and dependency resolvers . Each migration job is broken into manageable steps, and the output is a pull request .

Platform-Specific Migration Considerations

WordPress-to-WordPress Migrations

Managed platforms like WordPress VIP offer dedicated migration services with structured phases: preparation, kickoff, discovery, migration, QA, and launch . Key requirements include compatibility with the VIP File System and PHPCS checks for plugin compliance .

Critical Considerations:

• File System Compatibility: Media files on VIP are not stored locally—they use an API-backed read-only service .
• Launch Timing: Weekend launches are strongly discouraged due to lower traffic levels that can obscure performance issues .
• Testing Responsibility: The migration service handles the technical transfer, but the customer's development team is responsible for bug fixes and site updates post-launch .

CMS Migration

Kentico migration experts recommend a tiered approach :

• Tight Budget: Keep the existing frontend and only fix what breaks; use AI-assisted E2E tests to make it touchable later.
• Some Contingency: Treat the migration as a chance to modernize from the inside out—keep the visual design but clean up the JS/CSS stack.

AI in Practice: Teams have had good success using AI agents to refactor BEM + SCSS to more modern approaches, upgrade React class components to JSX, remove jQuery in favor of vanilla JS, and move from Webpack to Vite .

Design Principles for Code Migration Projects

Start with Production, Not the End: Going live early, even with a hidden or partially empty page, allows teams to understand performance and resource management before the full build is complete .

Prioritize Tests Over Refactoring: If the client is happy with the design, prioritize AI-generated E2E tests over underlying technology changes. This supports future upgrades and reduces the risk of regressions .

Use the Strangler Fig Pattern: Incrementally replace parts of the legacy application with new services, routing traffic gradually to minimize disruption .

Embrace the Unblocked Mindset: If a certain aspect of a task can't be finished, finish the rest and revisit it later. The goal is to never be blocked by something you can't directly fix yourself .

Treat the Migration as a Cultural Shift: Moving from low-code to code-first changes not just the technology but the team dynamics. It forces less technical team members to engage with the tools engineers use daily, lowering the understanding gap between teams .

Our Approach to Code Migration

We understand that code migration is about managing risk while achieving technical and business goals. Our approach combines:

Strategic Assessment: We evaluate your current codebase, identify the sources of technical debt, and recommend the right migration strategy based on your goals and constraints.

Incremental Rollout: We use the Strangler Fig pattern to migrate gradually, keeping the old system running while the new one is built and tested.

AI-Assisted Efficiency: We leverage AI tools to accelerate migration tasks—from code translation to documentation generation—while maintaining quality control through human oversight.

Testing and Validation: We prioritize E2E tests, data validation, and performance monitoring to ensure the migrated system works as expected.

Ongoing Support: We provide continuous maintenance, monitoring, and optimization to ensure the migrated platform remains healthy and performant.

Conclusion: Moving Forward Without Breaking What Works

Code migration is one of the most challenging disciplines in software development—but also one of the most rewarding. A successful migration transforms a codebase riddled with technical debt into a scalable, maintainable asset. The key is to approach it strategically: break it into manageable pieces, keep the old system running while the new one is built, and validate at every step.

Partner with a team that understands the nuances of code migration—the tension between client expectations and technical necessity, the value of gradual rollout, and the power of AI to accelerate the process.

Let's Build Your Migration Strategy

Ready to modernize your codebase without disrupting your business? Our team specializes in code migration and legacy modernization. Contact us today to discuss your project and discover how we can help you move forward without breaking what works.