What is a custom web application?
A web application is software you use in a browser, with nothing installed on the workstation. Custom means it is written for your business rather than configured out of an existing product: your rules, your vocabulary, your screens, and a database you own.
The difference from off-the-shelf software is not quality, it is fit. A general-purpose ERP asks you to adapt your organisation to its data model. A custom application starts from your organisation as it is, exceptions included — and those exceptions are often precisely what distinguishes you from your competitors.
Web application or brochure site: what's the difference?
The confusion is common, and it changes both the budget and which supplier you should be talking to.
A brochure site presents
Pages, content, a contact form, search visibility. The user reads. The value is editorial and marketing. A classic web agency does this well, often on WordPress.
A web application does work
Users log in, data is entered and transformed, permissions differ by role, rules calculate, exports run, other systems integrate. The user produces. The value is operational.
We don't build brochure sites. If that's your need, a web agency will serve you better and cheaper, and we'll say so in the first conversation.
When a custom web application is the right call
Four situations come up in almost every project we take.
A spreadsheet has become the production system
A shared file carries invoicing, pricing or planning. It works, until two people edit it at once, until a formula breaks with nobody noticing, or until the one person who understands it goes on holiday.
Off-the-shelf software covers 70% of the need
The rest lives in exports, manual rework and copy-paste between two tools. The real cost is not the licence, it's the hours spent every week bridging the gap by hand.
The process is your competitive advantage
When the way you work is what sets you apart, standardising it into a generic product erases exactly the thing that works.
Several systems need to talk to each other
ERP, CRM, accounting, logistics. The data already exists, it's just scattered. Here the application becomes a business layer on top of what you have, without replacing all of it.
And when it isn't the right call
If off-the-shelf software covers your need, buy the off-the-shelf software. If the tool serves one person, no-code is usually enough. If the process still changes every week, wait for it to settle: building against a moving target costs twice, once to build and once to undo.
What "custom" actually means
Everyone uses the word. Here is what it should imply in practice, and what you should demand of any supplier.
You own the code
Rights to the code assigned to you, the Git repository in your name, hosting in your name. Without that, you are renting your production tool without knowing it.
Delivery in usable increments
A first version in production on a narrow scope, then additions. No six-month tunnel ending in the joint discovery that the requirement was misunderstood.
Tests on the paths that cost money
Not exhaustive coverage for the statistic, but a safety net over the things whose failure is expensive. That is what lets someone change the application in two years without holding their breath.
Another team can take it over
Reproducible development environment, automated deployment, documented architecture. The test is simple: can a team that did not write this code evolve it? If the answer is no, you bought a dependency, not software.
Our technologies
Go and Python on the server, TypeScript and React in the browser, PostgreSQL for data, deployed on Kubernetes or a managed platform depending on the size of the project. We also take over existing applications in PHP, Symfony and Node.js.
The technical choice is not a sales argument: it follows from your context, your in-house skills, and who will maintain the application in three years. If something falls outside what we do, we say so before taking the engagement rather than after.
What does web application development cost?
None of the agencies ranking for this search publish a rate. Here are ours. A custom web application starts at €5,000, and that figure buys a first scope genuinely in production, not a mockup.
| Service | Price | What it covers |
|---|---|---|
| Custom web application | from €5,000 | Design, development, testing and release of a first genuinely usable scope. Fixed price per milestone set at scoping, not open-ended time and materials. |
| Development day | €800 | Beyond the initial scope: new features and changes as they come up. |
| Code audit | €2,500 fixed | Only if an application already exists. Full report on architecture, technical debt and security, with no commitment to what follows. |
| Maintenance | from €1,600 per month | After release: fixes, changes, version upgrades. Two days a month, adjustable. |
What moves the budget
- The number of real business rules, not the number of screens. Thirty simple screens cost less than one pricing screen with fifteen special cases.
- Integrations. A documented API connects quickly. An old ERP with no API is paid for in days of exploration, and it is the line most often underestimated in quotes.
- Migrating existing data. Years of spreadsheets almost always contain duplicates, mixed formats and unwritten exceptions, each of which needs a decision.
- The number of user roles. Every role adds permissions, screens and cases to test.
€5,000 is a floor, not an estimate of your project: it's the point below which a custom web application doesn't make sense, and it's often more. We don't give an upper range before understanding the scope, because a number quoted too early is wrong in both directions. Scoping produces a fixed price per milestone, and you can stop at the end of any milestone.
How long does it take to build a web application?
We aim for a first version in production on a narrow scope in weeks, not months. That's not a promise of speed, it's risk reduction: an application used by real users early exposes design mistakes while they are still cheap to fix.
What stretches a project is rarely the development. It's decision time on the client side, access to existing systems, and the availability of the people who know the business. We say so at scoping, because it's the part of the schedule we don't control.
Frequently asked questions
What is an application development agency?
A supplier that designs, builds and maintains custom applications for other companies, as opposed to a software vendor selling its own licensed product. The deliverable is software you own. The distinction worth checking is this: a web agency builds sites, an application development agency builds business software. The two trades often share a name and do not share the same skills.
What does web application development cost?
At Reflekt Lab a custom web application starts at €5,000, for a first scope genuinely in production. Beyond that the day rate is €800, and after scoping we commit to a fixed price per milestone. The total depends on the number of business rules, the integrations required and the migration of existing data, not on the number of screens. If an application already exists, the upfront code audit is €2,500 fixed.
What is the difference between a web application and a website?
A website presents information: the user reads. A web application processes information: the user logs in, enters data, triggers calculations and produces a result. Technically that means user accounts, permissions, a business database and integrations. Which is why the budgets are not comparable.
How long does it take to build a web application?
We aim for a first version in production on a narrow scope within weeks, then additions in increments. The factor that stretches projects most is not development but decision time and access to existing systems, which we cost explicitly at scoping.
Do we need a written specification before starting?
A useful document is enough; an exhaustive one is often counterproductive. We need to understand the current process, the business rules and the exceptions, plus what success means. We write that part with you during scoping if it doesn't exist yet.
Who owns the application's code?
You do. Rights to the code assigned to you, Git repository and hosting in your name. This is what determines whether you can change supplier one day, and it's settled in the contract, not at the end of the project.
Wouldn't a no-code tool be enough?
Often yes, and we say so when that's the case. No-code suits a tool serving a small team, on a stable process, with no hard security constraint. The limits arrive when you roll out across the organisation: per-user pricing, fine-grained permissions, integration with your company directory, and the difficulty of leaving the platform afterwards.
What happens after go-live?
An application in production needs fixes, changes and version upgrades. We offer maintenance from €1,600 per month for two days of work, or we train your in-house team to take the product over. Both are legitimate and we have no interest in making you dependent.
Do you work with companies outside Bordeaux?
Yes. We're based in Bordeaux and work across France and internationally, with a presence in Sydney. Projects run remotely, with time on site where it earns its keep, particularly for scoping and user training.
Can you take over an application that's already started?
Yes, it's a significant part of what we do. The entry point is a €2,500 fixed-price code audit that says what's sound, what needs work and what that amounts to in days. The precondition is holding the rights to modify the source code.
Got a business application project?
Describe the process you want to support and the tools already in place. We'll tell you honestly whether off-the-shelf software would do the job, and if not, what the project involves.
