React & Next.js Development

React and Next.js have become the gold standard for building fast, interactive, and scalable web applications. React's component-based architecture and Next.js's server-side rendering, static generation, and API routes make them ideal for projects that demand exceptional performance and developer experience. Kosmoweb's development team specializes in building production-grade React and Next.js applications for businesses in the Czech Republic and internationally.

We use React and Next.js for a wide range of projects, from corporate websites with complex content requirements to full-featured web applications and SaaS platforms. Next.js's built-in optimization features, including automatic code splitting, image optimization, and incremental static regeneration, ensure your site loads fast and scores well on Core Web Vitals metrics that Google uses for ranking.

Choosing between React and Next.js versus other options like WordPress depends on your project's complexity and goals. Our guide to WordPress versus custom development can help you evaluate which approach makes sense. For projects that require dynamic data, real-time features, complex user interfaces, or tight integration with backend systems, React and Next.js are typically the superior choice.

Our React and Next.js developers in Prague write clean, tested, and well-documented code that is easy to maintain and extend. We follow best practices for state management, API design, authentication, and deployment. Whether you are building a new product from scratch or modernizing an existing platform, we deliver solutions that are fast, scalable, and ready for the future. Ongoing support ensures your application evolves with your business.

React and Next.js are overkill for a five-page brochure site with one contact form. A static HTML/CSS/JS build or a WordPress site with a decent theme delivers the same user-visible result at a third of the cost, in a third of the time, and the client can edit content without a developer. The React advantage only emerges when interactivity, data complexity, or scale enters the picture. We have walked clients away from Next.js into WordPress more than once when the actual requirements did not justify the tooling — and saved them €3,000-6,000 in the process. Right-sizing tech to need is part of the job.

Where React and Next.js genuinely win: dashboards with real-time data and complex state, SaaS products with user authentication and role-based access, marketplaces with two-sided matching logic, configurators with hundreds of dependent options, complex e-commerce above the limits of off-the-shelf platforms, content sites needing top-tier performance, and any product where the frontend interaction model is itself the differentiator. The development velocity advantage compounds over time: a well-architected Next.js codebase with TypeScript, testing, and CI/CD lets a team ship features twice a week without breaking production. WordPress codebases rarely sustain that pace beyond year one.

Next.js 15 (released October 2024) shifted the architectural defaults significantly. The App Router with React Server Components is now the recommended approach: server-side rendering happens at the component level, not the page level, meaning interactive parts ship JavaScript while static parts ship zero JS. Turbopack is the default dev bundler, with cold-start build times 50-80% faster than Webpack on real projects. Server Actions handle form submissions and mutations without separate API routes, simplifying the code substantially. We have migrated a few CZ client projects from Pages Router to App Router in 2025 — non-trivial work, but the performance and developer experience gains are real.

Per-page rendering strategy is the single most impactful architectural decision in a Next.js project. Static generation (SSG) for marketing, docs, and blog routes — pre-built at deploy, served from CDN, TTFB under 100ms. Incremental Static Regeneration (ISR) for content that updates daily or weekly without triggering a full deploy: product listings, category pages, content collections. Server-side rendering (SSR) for personalized routes: dashboards, cart, account, anything depending on the logged-in user. Client-side data fetching for interactive widgets where staleness is acceptable. Getting this mix right is the difference between a Next.js site that flies and one that runs at 800ms TTFB everywhere.

TypeScript on any non-trivial React project pays back its setup cost within the first month. The obvious wins: type safety catches a category of bugs at compile time that would otherwise surface as production incidents. The less obvious but more valuable wins: refactoring confidence (rename a prop, every consumer updates or errors), IDE autocomplete that actually works because the types are real, and faster team scaling because new engineers can read the type signatures and understand the contract without reading the implementation. We use TypeScript strict mode on every Next.js project — the friction in the first week is real, the velocity gains in months 3-12 are larger.

SEO with Next.js is a solved problem when you set up rendering correctly. Marketing pages as full SSG (next export style or output: 'export' for fully static deployment), content pages as ISR with revalidate intervals matching update cadence, personalized routes as SSR. Metadata API handles title, description, OpenGraph, and JSON-LD at the layout or page level. Sitemap generation via next-sitemap or the built-in MetadataRoute. Image optimization through next/image automatically generates responsive variants and AVIF/WebP. The result is sites that pass Core Web Vitals effortlessly and that Googlebot indexes without quirks — which is the opposite of older client-rendered React SPAs.

Vercel is the default Next.js host because they built Next.js — first-party support, automatic ISR cache invalidation, edge functions, preview deploys per PR. Pricing scales fast above the Hobby tier (€20/seat plus bandwidth at €40/100GB), which surprises some teams at scale. Cloudflare Pages is cheaper and faster at the edge but requires more work to get full ISR working. Netlify is the established middle ground. For Czech clients price-sensitive at scale, we sometimes self-host on a €15-30/month VPS with PM2 and Cloudflare in front — works fine for sub-1M monthly visitors and saves €2,000-5,000/year vs Vercel Pro at scale.

Recent case: a Prague-based B2B services company on aging WordPress migrating to Next.js. Eight weeks of work, €11,800 in EUR, including content migration, redesign, and proper redirect mapping. Results six months post-launch: LCP from 3.6s to 1.1s, organic traffic +47% (because of better CWV scores and content depth, not new content), conversion rate from 1.8% to 2.9%, and post-launch maintenance dropped from €450/month to about 2 hours/quarter. Not every WordPress site needs to migrate, but when the maintenance and performance pain is real, the math works out within 12-18 months.