Legacy CMS to Next.js + Supabase Migration

ExpressionEngine served its purpose. MODX was genuinely innovative for its era. That custom PHP CMS your agency built in 2011? It worked. But "worked" is past tense, and that matters.

These platforms share a common trajectory: dwindling plugin ecosystems, security patches that arrive months late (or never), developers who've moved on, and performance scores that make Google's Core Web Vitals look like a horror film. You're paying premium hosting costs for servers that struggle to break 2-second page loads while a static site on a £20/month plan runs circles around you.

We've migrated ExpressionEngine sites with 15,000+ entries, MODX installations running 40+ custom snippets, and bespoke PHP CMS platforms with undocumented database schemas. Every one of them now runs on Next.js with Supabase, scores green across all Core Web Vitals, and costs less to host than the legacy stack did.

Why ExpressionEngine and MODX Migrations Fail

Most agencies treat a CMS migration like a redesign project. They build a pretty new site, do a CSV export, bulk import, set up some redirects, and call it done. Then you watch your organic traffic drop 40% over six weeks.

Here's what actually goes wrong:

Content Modelling Mismatch

ExpressionEngine's channel fields and MODX's template variables don't map cleanly to modern content structures. A "textarea" field containing HTML with inline styles, embedded images with relative paths, and custom shortcodes needs intelligent transformation — not a find-and-replace script.

URL Structure Fragmentation

Legacy PHP CMS platforms love generating URLs with parameters, category prefixes, and date-based structures that don't match modern routing conventions. Miss a single redirect pattern and you've got a 404 page where your highest-traffic landing page used to be.

Template Logic Buried in Content

MODX chunks and snippets, ExpressionEngine's template tags, custom PHP includes — these aren't content. They're presentation logic that got tangled into your database over a decade of organic growth. Separating content from display logic is the actual hard work of migration, and it's the part most agencies skip.

Authentication and User Data

If your legacy CMS handles member logins, custom user roles, or gated content, you can't just ignore that data. Password hashes need migrating, or users need a graceful re-authentication flow.

What Next.js + Supabase Actually Gives You

This isn't a marginal upgrade. It's an architectural leap.

Next.js for the Frontend

Next.js gives you static generation for content pages (sub-100ms TTFB), server-side rendering for dynamic routes, React Server Components for complex layouts without client-side JavaScript bloat, and incremental static regeneration so your content team publishes changes that go live in seconds without a full rebuild.

Your Lighthouse scores jump from the 45-65 range to 95-100. Not because of tricks — because the architecture is fundamentally faster.

Supabase for the Backend

Supabase provides a PostgreSQL database with a REST and GraphQL API out of the box. Row-level security handles permissions without middleware. Real-time subscriptions power live features. Built-in auth handles everything from email/password to OAuth providers. Edge functions handle server-side logic at the CDN edge.

For most legacy CMS migrations, Supabase replaces the entire backend stack: database, authentication, file storage, and API layer. One platform, one bill, no server maintenance.

Headless CMS Integration

For content teams who need a familiar editing interface, we integrate Sanity, Payload CMS, or Storyblok as the editorial layer. Content editors get a modern UI. Developers get structured APIs. Supabase handles everything that isn't pure content: user data, application state, analytics, form submissions.

Our Migration Process

We run a five-phase process built specifically for legacy PHP CMS platforms. No big-bang cutovers. No crossed fingers.

Phase 1: Deep Audit (Week 1-2)

We crawl your existing site completely. Every URL, every content type, every template, every redirect already in place. We map your ExpressionEngine channels or MODX resources to a modern content schema. We document custom functionality — search, forms, member areas, e-commerce hooks, third-party integrations.

Deliverable: a migration specification document with content model mappings, URL redirect map, and functionality inventory.

Phase 2: Infrastructure Build (Week 2-4)

We set up the Next.js application, configure Supabase (database schema, auth rules, storage buckets), and deploy to Vercel or Cloudflare Pages. CI/CD pipeline, preview environments, staging domain — all configured before any content moves.

Phase 3: Content Migration (Week 3-6)

Custom migration scripts extract content from your legacy database, transform it (cleaning HTML, resolving image paths, converting shortcodes to structured data), and load it into the new system. We run this iteratively — migrate, validate, fix edge cases, re-run.

For ExpressionEngine, we connect directly to the MySQL database and parse channel data with field type awareness. For MODX, we handle the resource tree, template variables, and chunk references. For custom PHP CMS platforms, we reverse-engineer the schema and build bespoke extractors.

Phase 4: Frontend Build (Week 4-8)

Next.js pages and components built to match (or improve) your existing design. Every page template from the legacy site gets a modern equivalent. We optimise images, implement responsive layouts, and make sure every page hits green Core Web Vitals before launch.

Phase 5: SEO Cutover and Go-Live (Week 7-10)

This is where migrations succeed or fail. Our cutover process:

• 301 redirect map deployed and tested against the full URL crawl from Phase 1
• XML sitemaps regenerated and submitted to Google Search Console
• Canonical tags, hreflang, and structured data preserved or improved
• Real-time monitoring for 404 spikes, crawl errors, and ranking movement for 30 days post-launch
• Zero-downtime DNS cutover — legacy site stays live as fallback until we confirm clean indexing

We guarantee no ranking loss attributable to the migration. If Google drops a page because of a redirect we missed, we fix it same-day.

SEO Preservation Strategy

SEO preservation isn't a phase — it's a constraint that governs every decision throughout the project.

We export your full backlink profile and cross-reference it against the redirect map. Internal links are updated programmatically, not manually. We preserve page authority by maintaining URL structures where possible and implementing proper redirect chains where they change.

Next.js gives us server-side rendering for crawlers, which means Google sees fully-rendered HTML at first request — no JavaScript rendering delays that plague SPA migrations. Combined with sub-300ms TTFB from edge deployment, your pages get crawled faster and indexed more completely than they ever were on the legacy stack.

Timeline and Pricing

Transparent pricing means you know the range before the first call.

Project Size	Content Volume	Timeline	Investment
Standard	Up to 500 pages	6-8 weeks	£12,000 - £25,000
Mid-scale	500-5,000 pages	8-12 weeks	£25,000 - £55,000
Enterprise	5,000+ pages, custom functionality	12-20 weeks	£55,000 - £120,000

Pricing includes the audit, migration scripts, Next.js build, Supabase configuration, SEO cutover, and 30 days of post-launch monitoring. No hourly billing surprises. Ongoing hosting on Vercel + Supabase typically runs £50-200/month depending on traffic — a fraction of legacy server costs.

100% Green Core Web Vitals Guarantee

Every page we ship passes Google's Core Web Vitals assessment with green scores across LCP, INP, and CLS. Not on a fast connection in a lab test — in the field, measured by real users via CrUX data.

If any page fails CWV within 90 days of launch due to our implementation, we fix it at no additional cost. We can make this guarantee because the Next.js + Supabase architecture, deployed to edge CDNs, is inherently fast. We're not fighting the platform to get good scores — the platform delivers them by default when built correctly.

UK and US Coverage

We work with teams across the UK and US, with deployment optimised for both markets. Vercel and Cloudflare edge networks ensure your site loads fast whether your users are in London, Leeds, Los Angeles, or Louisville. All projects include GDPR-compliant data handling for UK/EU audiences and SOC 2-aligned practices for US enterprise requirements.