A static HTML site migrated to a real Next.js foundation, with the visual identity kept intact.
Overview
A personal trainer's site, migrated from a single hand-built HTML file to a proper Next.js application without changing how the site looks or reads to a visitor.
The existing site worked, but its single-file structure had no path forward — no type safety, no component reuse, and no realistic way to add the six-language support the client needed.
Challenge
A real coaching session, Cluj-Napoca.
Approach
Rebuilt the entire technical foundation — routing, components, a real internationalization system, a theme toggle — while holding the existing visual design fixed as the spec, then verified the result by actually clicking through it rather than trusting a clean build.
The site, as built
Design & Development
- A six-language system built from scratch
- Romanian, English, Hungarian, French, Spanish, and German, switchable client-side with no layout reflow between languages.
- A theme toggle that respects the visitor's system preference
- Light and dark modes, persisted across visits, defaulting to whatever the visitor's system already prefers until they choose otherwise.
Technical Decisions
- A bug only real interaction testing could catch
- A security header shipped in an earlier pass was silently blocking every interactive script on the site — the build stayed green and every type check passed, because neither checks whether a click actually does anything. Caught only by clicking through the live site.
Results
Initial page weight
2237 KB514 KB
The original single-file site shipped 2.2 MB on first load, nearly all of it unoptimised imagery; the rebuilt site ships 514 KB. Median of three loads, cache disabled.
Cumulative Layout Shift
~0
Measured on the rebuilt site. Largest Contentful Paint is deliberately not claimed here — the original was only measurable from local disk, and comparing that against a live site over the network would flatter the result rather than describe it.
- Role
- Architecture, Development, Migration
- Stack
- Next.js, TypeScript, Tailwind CSS
- Year
- 2026
- Industry
- Fitness & Personal Training