Custom web app development: when to build one and how it works

What a custom web app is and when it makes sense

A custom web app is a browser-based program people work in every day: entering data, approving, searching, generating documents. Unlike a website, it is a tool, not a showcase: an internal order or reporting system, a client portal, a specialised calculator.

Custom software makes sense when:

• ready-made software covers only part of the process and the rest is manual,
• data is copied between spreadsheets and tools, and errors creep in,
• you need a feature no product offers, or only in an expensive plan,
• you want control over where data lives and who can access it.

The deciding factor is its own interface. If you only need to move data between applications, send alerts or import a spreadsheet, with nobody clicking through it, see automation and API integrations.

Who it suits and who it does not

It suits businesses that know which problem they are solving and how the work is done today. No finished specification is needed; it comes out of the analysis. What is needed is someone who knows the process.

It also suits cases where a backend exists and the frontend, the part users see, is missing. webrocks has done this on internal PPC and reporting tools: turning a visual design into React and connecting it to an existing backend.

It is not the right fit if:

• you want a site that presents your business and collects enquiries; for that, see business website,
• you need a tool working directly on top of other websites, where a custom Chrome extension often fits better,
• you want an online shop built from scratch, which webrocks does not do.

How custom web app development works

1. Requirements analysis

The first step clarifies who will use the app, for which tasks and with which data. The result is a feature list split into what the first version needs and what can wait. This step shapes the price more than any other.

2. Architecture design

This decides where data lives and whether the app needs a server, sign-in and connections to other applications. Not every app needs a server. An example is Pagami.cz, a free invoicing tool for Czech sole traders made by webrocks: data stays in the browser in IndexedDB (a database inside the browser), company details are filled in from the Czech ARES business register, and invoices include a QR payment code and PDF export.

3. Development in stages

The app is built in smaller parts you can try out. Gaps in the brief show up early.

4. Testing and handover

Before handover, the app is run through real scenarios with real data, then deployed and handed over with what is needed to keep it running.

Desktop and mobile: Electron and React Native

Most internal tools are fine as a web app: it works on computer and phone, needs no installation and everyone gets updates at once.

For an installable app with its own icon and window, consider a PWA (progressive web app). It can work offline, with one codebase for every device. Before deciding, check that the features you need work on the devices people actually use.

Electron is a framework for building desktop applications with JavaScript, HTML and CSS. It bundles Chromium and Node.js, and one app runs on Windows, macOS and Linux. It makes sense when people want a standalone program rather than a browser tab.

A custom mobile app can be built with React Native. For a new app, its documentation recommends the Expo framework. Choosing between a PWA and a native app depends mainly on which phone features the app needs. According to web.dev, a PWA can also be listed in app stores, so that alone is no reason to go native.

What you get

• a working app within the scope agreed in the analysis,
• the source code on the terms set in the contract,
• the app deployed to hosting, or ready to deploy on your own server,
• notes on running, deploying and configuring the app,
• a list of what was left out of the first version.

What to watch out for

A first version that is too big. A common mistake is wanting everything at once. A smaller one reaches users sooner and shows what they really need.

A server where none is needed, or the other way round. React recommends starting new apps with a framework such as Next.js, and these can also produce a purely static app with no server. A Next.js static export, however, lacks Server Actions, redirects from the config and default image optimisation. If the app needs these, static hosting is not enough and it needs a Node.js server.

Where the data lives. Browser-only data means privacy and no server costs, but only one device sees it and the user handles backups. Server data needs sign-in, backups and access management.

Maintenance. Libraries and platforms age. According to the release schedule, Node.js 20 reached its end of life on 30 April 2026, and the Node.js project recommends only long-term support (LTS) versions for production. Plan for updates even if the app itself does not change.

When not to build a custom app

If a ready-made tool covers most of the process, adopting it is cheaper. The same goes for a shared spreadsheet whose only problem is that nobody keeps it updated. An app will not fix a poor process; it only speeds it up.

A third option often sits in between: keep the spreadsheet and add a script that checks data, moves it or sends an alert.

How much a custom web app costs

In the price list, a web app is priced by scope and covers requirements analysis, architecture design, custom development and testing. The indicative hourly rate in the price list is from 500 CZK/hr. The price depends on the scope and complexity of the project.

The price goes up with:

• several user types with different permissions,
• integrations, especially poorly documented ones,
• a desktop or mobile version alongside the web app,
• a brief that keeps changing during development.

It comes down with a clearly defined first version, a single user type and no server of its own where possible. If you know what the app should do, describe it in an enquiry. You will get a reply within 24 hours.

Frequently asked questions

Which technologies does webrocks use?

JavaScript, React, Next.js and Node.js; Electron for desktop and React Native for mobile. The choice follows what the app needs.

Who owns the source code?

Ownership and licensing of the code are agreed in the contract before development starts, including repository access and whether you may continue with another supplier. Third-party libraries have their own licences.

How long does development take?

It depends on the scope of the first version, the number of integrations and how quickly answers and feedback come back. A timeline estimate makes sense only after the requirements analysis.

How does maintenance work after handover?

It is worth agreeing maintenance separately: library and platform updates, bug fixes, small changes. Without it the app keeps running but gradually ages.

Custom web app or ready-made system?

A ready-made system is quicker and cheaper to start with if it covers most of the process. A custom app pays off when the ready-made one needs constant workarounds or lacks a feature you cannot do without.