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About

The studio behind the work

CompletApp is a full-stack product studio based in Budapest, building cross-platform apps, web apps, and custom websites, with real backends behind them and the API integrations that connect an app to the systems a business already runs.

11+

Years building

10+

Products shipped

70+

Apps published

3,000,000+

Combined downloads

24h

Reply time

János Kiss, founder of CompletApp

Hi, I am János

I am János, based in Budapest, Hungary, and currently the solo force behind this studio. I build with full-code Flutter, and for the web with modern tools like React and Astro. AI from OpenAI and Claude goes in where it earns its place.

Most of what I build starts from a blank page: an app, a backend on Supabase or Firebase underneath it, and nothing else in the way. That is the right answer more often than people expect, and it is how most of my work ships. Other projects arrive the other way round. The company already runs on something, and the job is software for the people doing the work that fits around that system instead of replacing it. You will find both kinds in my portfolio. Part of my job is telling you which one you actually need.

I am not a developer in the traditional sense. I am more of a business-minded person who uses technology as a tool to help others bring their ideas to life. My strength lies in turning concepts into functional, user-friendly apps that make a real impact. I own several apps that are live in the stores today, and together they have reached millions of downloads.

My journey into app development started in a completely different field: I am originally a biologist. My passion for building apps began back in 2015, and it has only grown stronger over the years. Since I never formally studied programming, I started in the world of no-code and became highly skilled with FlutterFlow. It was a fast, effective way to build and validate real products, and as my clients grew, so did their needs.

Beyond app creation, I have invested significant time into understanding the app business, from marketing and growth strategies to UI and UX design. It is all part of my commitment to delivering high-quality products, whether they are my own or for a client.

My ultimate vision is to help millions of people improve their lives in some way. Whether through my own apps or by helping others turn their ideas into reality, I am dedicated to making a positive impact, and I am excited to keep growing and sharing this journey with you.

How I work

Business first

Technology is a tool. Every decision serves your users and your bottom line.

Ship fast, ship right

Rapid delivery without cutting corners on quality or performance.

Full ownership

On full payment, all rights to your product and its code are yours.

Honest and direct

Clear scope, fixed price, daily progress, and no jargon.

Tech stack

Built on a modern, AI-native stack

The tools we use to design, build, ship, and scale your product.

Flutter

Mobile

React

Web

Astro

Web

WordPress

Web

TypeScript

Tooling

Tailwind CSS

Tooling

Firebase

Backend

Supabase

Backend

OpenAI

AI

Claude

AI

Stripe

Payments

RevenueCat

Payments

Resend

Comms

OneSignal

Comms

Vercel

Tooling

Cloudflare

Tooling

Common questions

I do, with AI tooling as a force multiplier. Design, code, backend, and launch run through one pair of hands, which is exactly why scope stays honest and nothing gets lost between departments.

That is what the guarantees are for: fixed scope and price in writing, milestone-based delivery, and if you are not happy after the first milestone you walk away owing nothing. You also own 100% of the code on full payment, so you are never locked in.

Budapest, Hungary (CET). Clients are worldwide, and work runs in English or Hungarian.

Send a few sentences about your idea through the contact page. You get a reply within 24 hours and a free 30 minute discovery call, and after it a written proposal if we are a fit.

Let us build yours

Tell me about your idea and I will map out the first step.

Start a project