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Custom software development: the tool no product sells you, with the source code in your name.

A written scope, acceptance criteria, EU hosting by default, and the overrun risk on our side. When a product you can buy already fits, we tell you instead of building.

Tell us about your projectA 20-minute video callBuild or buy first

What custom software costs, before anyone has seen your project

Two grids published by French development agencies in 2026, excluding VAT. Per row, from the lowest to the highest figure of the two.

Shape of projectMarket range
A simple internal tool, first scope5000 to 50 000 €
One published grid says 5000 € to 15 000 €, the other 15 000 € to 50 000 €.
A business application20 000 to 150 000 €
One published grid says 20 000 € to 60 000 €, the other 40 000 € to 150 000 €.
A multi-user platform or SaaS50 000 to 250 000 €
One published grid says 50 000 € to 150 000 €, the other 80 000 € to 250 000 €.
A custom ERPfrom 80 000 €
One published grid says 80 000 € to 250 000 €, the other 100 000 € and above.

Market ranges, not our rates. Our price comes out of a paid scoping on your real data, then holds: a fixed fee for a closed scope.

Where these figures come from: the method, read on September 28, 2026

Two price grids published in 2026 by French development agencies, in euros; the figures are quoted as published, not converted. On the same row the two grids can sit a factor of three apart, because they do not put the same thing behind the same name. What moves a project from one row to the next is the number of integrations, the state of the data to bring across and the level of finish, almost never the number of screens.

What is custom software development?

Software written for one organization's process, owned by that organization and hosted where it decides. In British usage, bespoke software development.

With us that means an EU data center unless you ask otherwise, accounts in your name from the first day, and a fixed fee for a closed scope with written acceptance criteria. If the estimate turns out wrong, our margin absorbs it, not your budget.

We have built national infrastructure this way for Expertise France in Cameroon, with the sources and the hosting under the client's control as a condition, and the whole software estate of Insight SiP, an electronic component manufacturer, on one architecture.

A hand typing on a laptop open on CSS code
Photo for illustration.

Most companies asking for custom software should buy instead.

Trial two or three products with the people who will use them. If one covers most of the need, buy it: the vendor patches it and absorbs regulatory change. Building earns its cost when your need falls outside the market.

The first question on every project here is whether it should be built at all. When the answer is no, we say so, and that conversation costs you nothing.

  • A vocabulary only your trade uses
  • Integrations with systems only you run
  • A process that is your advantage, or a sovereignty constraint

From a scope you can trust to a system you run without us.

No stage is a status meeting. Each one hands you something you keep.

  1. Short, paid

    A quote that rests on evidence.

    We open the hood first: your real data, the integration points, the edge cases that hurt. The scope is yours even if you take it elsewhere.

  2. Fixed fee

    Working software, cycle after cycle.

    Short cycles you can try. What is in scope is owed; anything new is a priced change you decide on.

  3. Before go-live

    Acceptance on the paths that break.

    A cancellation after payment, a corrupted import, two people editing one record, real data volumes.

  4. At handover

    Everything in your name.

    Source code, documentation written as we went, a decision log, credentials, and one person on your side trained to run it.

A Liège tramway at a stop, trees and overhead lines along the track
3000resident reports collected, 24 municipalities

Case study, over the duration of the works

Liège metropolitan area, Belgium

A tramway program, followed by its residents.

The problem
Resident and field reports to handle across a multi-year infrastructure program, in 24 municipalities with their own rules, on a timetable the works would not wait for.
What was delivered
A reporting platform we already ran, adapted to the Belgian context rather than rewritten: a mobile reporting app and dashboards for the technical services, covered by the Belgian press at launch.
All case studies

What you sign for custom software, in short.

Price
A fixed fee for a closed scope, set after a paid scoping. We sell a deliverable, not days.
Scope
Written, with acceptance criteria. A change is priced and decided, never absorbed in silence.
Overrun
If our estimate was wrong, it is our margin that pays, not your budget.
Hosting
An EU data center by default, on accounts opened in your name.
Ownership
Source code, documentation, credentials and accounts transfer at delivery, without restriction.
The commitments, with the limit of each

Who builds your software, and who can take it over.

Three senior engineers, two of whom have worked together for more than twenty years. The people you meet at scoping are the people who write the code, and everything is documented so someone who was not in the room can run it.

  • Laurent Tulpan, founder of Coeur du WebLaurent, founder and CTORuns the scoping, writes the scope and defends the architecture choices.
  • Clairmont, technical leadClairmont, technical leadArchitecture, backend, infrastructure and integrations with the systems you already run.
  • David, frontend leadDavid, frontend leadDesigns the interfaces, so the tool is still pleasant to use two years later.

Cost, ownership, hosting: before you commit.

When is custom software the wrong answer?

Whenever a product on the market covers most of the need and the rest can be configured or worked around without pain. Then buy it: the vendor maintains it, patches it and absorbs regulatory change, and you pay for configuration rather than construction.

Building earns its cost when the need falls outside the market:

  • a vocabulary specific to your trade
  • integrations with systems only you run
  • sovereignty constraints
  • a process that is itself a competitive advantage.
What does custom software development cost on average?

There is no meaningful average, because two projects with the same name can sit a factor of five apart.

The two grids published by French agencies and quoted at the top of this page put a first, simple scope at 5000 € to 15 000 € or 15 000 € to 50 000 €, and a business application at 20 000 € to 60 000 € or 40 000 € to 150 000 €.

Those are market ranges, not our rates. What moves a project between rows is the number of integrations, the state of the data to migrate and the level of finish.

What makes a custom software budget overrun?

Five things, and only the first is obvious:

  • A scope nobody wrote down, so every meeting adds an obvious feature.
  • Data migration assumed to be an export and an import, when the records are inconsistent and duplicated.
  • An integration discovered halfway, which costs several times what it would have cost if designed in.
  • Load requirements nobody stated, surfacing on the day success arrives.
  • Maintenance budgeted at zero.
Who owns the code and the documentation?

You do, and it is written into the contract before anything starts. Sources, documentation, credentials and accounts transfer at delivery without restriction on use.

That single clause removes the most common trap in this market, the vendor whose knowledge lives only in their own head. If a supplier hesitates on that point, you have learned something important.

Where will the software and its data be hosted?

In an EU data center by default, on accounts opened in your name, unless you ask for something else.

For a US or UK company that is often the point: data about people in Europe stays under the rules it was collected under, and a deletion request reaches every copy because we designed where the copies are.

If your users and data are all outside Europe, we host where it makes sense and say why.

Can the work be delivered in stages to spread the budget?

Yes, and it is often the better approach. We ship a foundation that is useful on its own, then add capability in waves, each priced separately. You spread the spend, validate the value at every step, and keep the option to stop or change direction.

The one condition is that the first architecture is designed to receive what comes next, a decision made at scoping, not later.

And when you need someone senior to decide first?

Lead and modernize

Someone senior to decide, on a bounded mandate.

Closer to your case

All services

Describe the need. You will know in 20 minutes whether to build it.

Custom software, a product off the shelf, or nothing at all for now: we tell you which, and why.

Tell us about your project

A 20-minute video call