Cross-Platform App Development

Cross-platform app development means building one app from a single codebase that runs on both iOS and Android, instead of writing two separate native apps. It suits founders and businesses that need to be on both app stores without paying for two builds. CompletApp is a Budapest-based product studio that builds these apps with Flutter, working in Hungarian and English at a fixed scope and a fixed price.

In practice you get one app that looks and feels native on both iPhone and Android, and because it is built once, it costs less to make and less to keep running. We design, build, and ship it end to end, and Flutter is what lets a small team move at the speed of a large one without cutting corners on quality.

Building twice, once for iOS and once for Android, means two builds, two release schedules, and every future bug fix done twice. We take a different route: one Flutter codebase that compiles to genuinely native apps on both platforms. That means your users get smooth, responsive, platform-correct experiences, and you get a product that is faster to launch and cheaper to maintain for years.

We build full consumer and business apps end to end: onboarding and authentication, real-time data, offline support, push notifications, in-app purchases, and the polished screens that make people want to come back. Whether it is a content app, a marketplace, a social product, or an internal business app, we handle the whole stack from interface to backend so you have one team accountable for the result.

Two shipped examples. Frendex, a local services booking app, is live on the App Store and Google Play from one Flutter codebase, on phone and tablet, in Hungarian and English, with Supabase behind it and provider subscriptions running through RevenueCat. The Kids Games series runs its current generation on FlutterFlow, one codebase for iOS and Android, and its flagship title has passed 1 million downloads.

Every build starts with the outcome you care about, the thing the app needs to do for your users and your business, and we work backward from there into screens, data, and infrastructure. The result is an app that does its job well, not a pile of features nobody asked for.

Flutter draws its own interface, so the app runs at a steady 60 frames per second with crisp animations and consistent behavior on every device. We respect each platform’s conventions where it matters, gestures, navigation, and system integrations, so the app feels right at home on iOS and on Android. You ship to both stores at the same time, from the same source, with the same quality bar.

Native development is still the better choice in some cases, so here is the comparison in short:

If your product sits in that last cell, native is the better investment, and we will tell you so.

If your app needs to make money, we make that part work properly. We integrate Stripe for card payments and RevenueCat for subscriptions and in-app purchases, so renewals, free trials, upgrades, and refunds all behave correctly across the App Store and Google Play. We set up the products, the paywalls, and the receipt handling so revenue flows reliably and your accounting stays clean.

We agree the full scope and a fixed price before any code is written, so there are no open-ended bills and no surprises. We then deliver in short, reviewable stages, so you see real progress every week and can steer as the app takes shape. You stay close to the work without having to manage it.