Web application development: a custom web app on your own data
Have a web application built when a process runs through spreadsheets and email that no package covers. Build it on the systems you already run, start with one process, and keep the code.
A web application is software your people use in the browser: a planning tool, a portal, a dashboard, an internal tool that replaces a spreadsheet nobody trusts any more. For an organisation with its own IT team or ICT partner the question is rarely whether it can be built. It is which process deserves it, which systems it reads from, and who runs it afterwards.
Last updated: 4 November 2026
A web application pays off where a process now runs through spreadsheets, email and copy-paste between systems, and no package covers it without workarounds. Build it on the data you already have in AFAS, Exact, SAP Business One, Dynamics 365 or your CRM, not as a second database. Start with one process and one group of users, prove it with real people, then extend. Crux Digits builds in three fixed-price steps (audit €2,500, Production-ready MVP €20,000, production from €50,000), works next to your ICT partner, and hands over all source code.
Web application, website or package: which one do you need?
| Option | Fits when | Falls short when |
|---|---|---|
| A package (SaaS off the shelf) | Your process is the same as most companies in your sector and the package covers it without workarounds. | You keep a spreadsheet next to it, or pay for modules you only half use. |
| A website or CMS | You publish information: pages, articles, a contact form. | Users need to log in, see their own data and change it. |
| A custom web application | The process is yours, it touches several systems, and people now bridge them by hand. | A package already does it well enough; then configure the package. |
What a custom web application usually is
- An internal tool that replaces a spreadsheet. Planning, quoting, order intake or quality registration that now lives in Excel files sent around by email. See also Excel automation.
- A portal for customers, suppliers or field staff. People log in and see their own orders, documents or work orders. For the customer side, see customer portal development.
- A dashboard on live data. Figures read straight from your ERP, WMS or MES instead of a monthly export someone rebuilds by hand.
- A SaaS MVP. The first sellable version of a product idea: one customer type, one core workflow, with sign-in and billing added when the workflow proves itself.
- AI inside the application, where it pays. Reading incoming documents, answering questions from your own knowledge base, or suggesting the next step to the user, with a person approving what matters.
Built on the systems you already run
- Your ERP and CRM stay the source. The application reads and writes through their own APIs: AFAS Profit connectors, the Exact Online REST API, the SAP Business One Service Layer, Dataverse for Dynamics 365. See API integration and extending your ERP.
- Sign-in with the accounts your people already have. Microsoft Entra ID for employees, roles per team, and a separate login for external users when a portal needs one.
- A modern, common stack. React and Next.js in the browser, Python with FastAPI behind it, deployed to your own Azure or AWS environment, so any competent team can maintain it later.
- Changes pass the source's own rules. An order or an address change goes through the ERP's validation, so the web app cannot create records your administration would reject.
Who does what: your ICT partner, your IT team and Crux Digits
| Area | Your IT team or ICT partner | Crux Digits |
|---|---|---|
| Hosting and environment | Runs the application in your own cloud environment, with backups and patches. | Delivers the application with documentation and a runbook for installation. |
| Identity | Manages the Entra tenant and who gets access. | Connects the application to that tenant and builds the roles. |
| ERP and CRM access | Provides an API user with minimal rights and a test environment. | Builds and tests the integration, including error handling and limits. |
| Change process | Approves releases through your change process and DTAP street. | Delivers a changelog, test results and a rollback plan with every release. |
| After go-live | Monitoring, incidents and first-line questions. | Hands over all source code and documentation; further development as a separate assignment, and managed support for the AI parts if you want it. |
What a custom web application costs and how long it takes
| Step | What you get | Duration | Price (excl. VAT) |
|---|---|---|---|
| AI audit | The process and systems mapped, build or buy assessed, and a scope with a fixed price for the next step. | 1 to 2 weeks | €2,500, credited against the MVP within 60 days |
| Production-ready MVP | The web application for one process and one user group, connected to your systems, with sign-in and roles, tested with real users. | 4 to 6 weeks | €20,000 |
| Production | All user groups, security testing, monitoring, documentation and handover of all source code to your organisation. | from 8 to 12 weeks | from €50,000 |
| On top | Hosting in your own cloud environment and any licences for the systems you connect. See our pricing. | ongoing | set by the vendor |
How a web application project starts
Do not start with a list of thirty features. Pick the one process that costs your people the most time today, usually the one with the most spreadsheets and the most emails asking where something is. Measure how long it takes now, so that after the first months you have a real comparison.
Then the MVP covers that process for one group of users, on the real systems, and goes in front of them within weeks. What they do with it decides the next step. One named senior engineer stays from scope to handover. For custom software in the wider sense, see custom software development.
Frequently asked questions
What does it cost to have a web application built?
How long does it take to develop a web application?
Who owns the source code?
Can the web application connect to our ERP?
Should we start with an MVP or build everything at once?
Is a web application the same as custom software?
Which process deserves its own web application?
Tell us which spreadsheet or which back-and-forth email costs your team the most time, and which systems it touches. We tell you whether a package is enough or which part needs a custom build.
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