Web App Development

Web app development means designing and building software that customers use in the browser: customer dashboards, marketplaces, content platforms and full SaaS products with accounts, subscription billing and an admin side. It is for founders and product teams who need a fast, reliable product that their own customers log in to. CompletApp is a Budapest-based product studio that builds these with React and Astro, in Hungarian and English, to a fixed scope and a fixed price.

Whether you need a focused customer product or a full SaaS platform, the brief is the same: it loads fast, works reliably, and is built to grow with your business.

A slow or fragile web app costs you users and trust every day it is live. We build the opposite: applications that respond instantly, hold up under real traffic, and stay clean enough under the hood that adding the next feature is straightforward rather than scary. You get software that earns its keep and keeps earning it.

We build the full range of customer-facing web applications: customer dashboards, marketplaces, content platforms, and complete SaaS products with accounts, billing, and the admin behind them. We take a project from idea and interface through to a deployed, working app that real users can rely on, so you have one team owning the whole thing rather than stitching freelancers together. Software your own staff use day to day is a different job, covered under internal business apps.

Two examples. Apartmanom is a property management platform that ships on the web as a host dashboard plus a booking widget guests use inside the host’s own site, live at the client’s own properties since June 2026. RankSpiral is an AI SEO content platform, live in 28 languages across 55 markets, where we worked as the founder’s product and technical partner.

Each build is shaped around the outcome first. We start from what the app must achieve for your users and your business, then design the screens, data, and infrastructure to deliver exactly that with nothing wasted.

We use React for rich, interactive interfaces and Astro to ship pages that load almost instantly, sending the browser only the code it actually needs. The payoff is real: faster load times and an app that feels effortless to use. Our own site is the example you can inspect: built on Astro, it scored 99 on desktop and 90 on mobile for performance in PageSpeed Insights in August 2026, and the case study shows how. Speed is not an afterthought we bolt on at the end; it is built into how we structure the app from the first commit.

When you need a product rather than a page, we deliver the whole picture: secure sign-up and authentication, subscription billing through Stripe, usage controls, and the admin tooling to run the business behind the app. We pair the front end with a solid backend on Firebase or Supabase so data, auth, and storage are dependable as you grow (the backend development page covers that layer). The architecture is designed to scale from your first users to your thousandth without a rebuild.

We agree the full scope and a fixed price before development starts, so you know exactly what you are getting and what it costs. We deliver in short, reviewable stages, putting working software in front of you early so you can react to something real instead of a slide deck. You stay in control without having to project-manage the build.