Custom Web Application: React + TypeScript + Supabase in 2026

Many projects begin as a marketing site and turn, six months later, into a full web application. The team needs a client portal, a dashboard, user roles, payments, notifications. The WordPress site or the Webflow landing page no longer holds. This shift from marketing site to app is not just a design question: it radically changes the technical stack, the hosting costs and the developer profile required. This article explains when to make the switch, why the React + TypeScript + Supabase combination has become a standard in 2026, and what a custom web application costs when you work with a freelance developer based in France.

I run CODRUM (SIREN 103 982 005, RCS Évry), a research firm in geomatics and web development based in Morsang-sur-Orge (91). The firm designs React web applications and SaaS products for startups and SMEs, with expertise reinforced by ongoing research within the Master 1 Geomatics G2M programme. The stack described here is the one we apply to client projects whose scope goes beyond a simple marketing site.

Marketing site or web application: where the line sits

A marketing site presents a company, its services, its team. The content is largely static, users are anonymous, and the objective is conversion (form, call, quote). A web application does the opposite: users authenticate, their data is stored and served back, business workflows run on the server. Client portal, booking platform, internal tool, marketplace, B2B SaaS: all of these fall under web application territory. The practical line comes down to three questions. Do you have identified users? Do you write data to a database? Must one user be prevented from seeing another user's data? Three yes answers mean you are leaving the marketing site domain and entering the app one.

Why this stack: React + TypeScript + Supabase

React remains the most widely used UI framework in the world in 2026, with a mature ecosystem (Next.js, Vite, Remix, React Query, React Hook Form) and a substantial talent pool. Compared with Vue or Angular, React offers the best coverage of developer talent in the Paris region, which matters if you ever need to bring the project in-house or recruit later. TypeScript adds type safety: bugs caused by wrongly passed arguments, missing fields or mistyped API responses are caught at compile time, not in production. On an application that crosses 10 000 lines of code, this is non-negotiable.

On the backend side, Supabase fulfils the Firebase role without its drawbacks. Open source, built on PostgreSQL (a real relational database, not NoSQL), with a native Row Level Security (RLS) system that pushes security rules as close to the data as possible. The pricing is predictable (Pro plan at 25 USD per month, no surprise bills as on AWS), and self-hosting remains possible if you ever want to leave the managed cloud. This is the decisive argument for founders who worry about vendor lock-in.

What Supabase covers out of the box

On a typical project, Supabase replaces five services that would otherwise need to be assembled by hand: Auth (email and password, magic links, OAuth Google, GitHub, Apple, MFA), Postgres with migrations and RLS policies, Edge Functions in Deno for server-side logic (Stripe webhooks, email sending, asynchronous processing), an S3-like Storage layer for files and images with access rules, and Realtime over websockets for live notifications or Notion-style collaboration. The pgvector extension additionally opens the door to AI features (semantic search, embeddings) without deploying a separate stack. One backend, one invoice, one administration console.

Reference architecture of a modern web app in 2026

On a typical client project, the architecture comes down to four building blocks: a React + TypeScript frontend deployed on Vercel (global CDN, automatic deployments on Git push, per-branch previews), Supabase Cloud for auth, database and Edge Functions, Sentry for frontend and backend error monitoring, and a domain on OVH or Cloudflare. For clients who wish to bring the frontend back onto OVH shared hosting, that path stays open: the frontend is built as a static bundle and Supabase remains reachable over HTTPS from anywhere. This frontend and backend separation makes the hosting migration painless on the day it becomes necessary.

Pricing and timelines for a custom web application

The orders of magnitude I apply on my projects: a web app MVP (authentication, two or three business screens, a database, deployment) starts at 4 000 € and ships in six to ten weeks. A full SaaS (multi-tenant, Stripe payments, admin dashboard, transactional emails, API documentation) starts at 10 000 € over three to six months. The final price depends on the number of screens, the integrations and the business complexity: a tailored quote is sent within 48 hours of a free initial call. Beyond that, the work shifts to team mode and billing becomes monthly. These prices include the technical stack, the frontend design, the automated tests and the production rollout. To discuss your project, please reach out through the contact page or browse my portfolio to see concrete examples of web applications delivered.

For a full breakdown of every service and price range, see the Services & Pricing page.