Your web development project

Support from start to finish

Support is in the DNA of Castelis for over 20 years. We are committed to advising you at every stage of your web and mobile development project, including and especially in the vision and design phases, upstream of development. The success of your web project depends on the quality of the design phase.

Our experts, coming from different web and design professions, help you make the right strategic and technological choices: definition of the need, specification, anticipation of the evolution… Moreover, we take into consideration the contexts of use of your IT solutions and the media used in order to adopt the mobile approach best suited to your project. Priority to the desktop and simple responsive web development? Use on tablets and smartphones implying a mobile-first or even mobile-only design?

Our engineers and developers are committed to respecting the best practices of web development to provide you with modern and efficient solutions.

Conseil et conception - Castelis

A tailor-made solution

For what kind of project

We intervene on web and mobile development projects of any size. A company can have specific needs involving a custom development regardless of its size. We are fully aware of the strategic stakes of your digital transformation projects for the growth of your company, its performance and the quality of your actions.

Enterprise platforms, intranet, extranet, web and mobile business applications, institutional and e-commerce websites, site factories… Your digital projects can take various forms, our teams handle the different technologies that allow us to give them life.

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UX / UI design and web development

Provide an optimal user experience

A new business application inevitably leads to changes in the habits of your employees, partners, customers and other users. In order to facilitate the change management and the adoption of the solution, the quality of the interface ergonomics is essential.

This is why Castelis surrounds itself with UX / UI experts in order to design the interface as well as possible, upstream of the development of the solution. To fluidify the user’s path, to reduce the number of steps, to structure the pages according to the rules of the art, to ensure the accessibility of the sites in multidevice, to optimize the attractiveness and the intuitiveness, to simplify the reading and the decision making… They give credibility to the brand by sending back a positive and modern image, at the same time as they work to offer a qualitative user experience.


Optimize SEO upstream of the design project by working on the site's marketing, branding, naming and SEO strategy. Before being designed, a site or an application answers strategic issues. The entire project must be defined upstream to ensure that the custom-developed site is consistent with the proposed offer, the target audience and the strategy developed.


Create a site that is compatible with different browsers and mobile and touch terminals, fast to load and compliant with web accessibility standards (such as the RGAA 4). Far from being a static tool, a website or a web application must adapt to the various possible uses, relative to the contexts of use but also to the particularities of the user, such as sight or hearing problems for example.


To propose a design conceived to provide a pleasant, intuitive and practical ergonomics. To achieve this, UX/UI designers take into account a vast combination of criteria requiring mastery of the use of colors and contrasts, the use of images and graphic elements, the choice of a legible typography consistent with the positioning of the brand and the expectations of users...


Facilitate the search for information by respecting the best practices of ergonomics and navigation. User paths must be fluid, the proposed actions intuitive and the expected use of the site clear. The pages must be structured and the information correctly listed and categorized in order to be found and consulted simply and quickly.


Reassure and convince users by designing a qualitative website, a real showcase for the brand. To give credibility to the brand and the website or web application, it is essential to choose the right tone in the content, to comply with the standards in place, such as the RGPD, and to ensure the relevance of the site in relation to research and user expectations.


Provide adequate functionalities to allow Internet users to easily find answers to their questions. This implies determining the services expected by users in order to ensure their satisfaction. But also to work on the differentiation and uniqueness of both the brand and the custom solution developed to promote its added value.

Experts en Services managés d’infrastructure Cloud et On-Premise

Agile method to manage your web projects

Optimize the costs and quality of your web development projects

We adopt an agile approach for your web and mobile development project. By dividing the project into different stages, based on objectives that allow us to advance our thinking and make informed decisions, we offer the necessary flexibility to the project to ensure customer satisfaction and that the solution really meets the needs.

It is also the best way to optimize design and development costs, by streamlining sprints and pooling development for common features. Intelligent reuse of code in the form of modules saves both time and money. Moreover, this approach is in line with our green IT approach and our permanent efforts to propose sustainable and eco-designed applications development.

Focus on microservices architecture

Ensure reliability and scalability of your custom solution

Our teams work with a modern and open source technical stack. Thanks to this, we develop reliable, state-of-the-art, scalable and preferably cloud-native software and business applications.

We favour web development based on a microservices architecture. In this way, we develop services in the form of modules that communicate with each other with independent APIs. It is then possible to add functionalities according to the necessary evolutions, to avoid the interruption of services on all the tools in case of failure or update, to simplify and accelerate the developments and to make the whole more readable for the developers, as opposed to the traditional monolithic architecture.

This microservices architecture, worthy heir of the SOA, allows to adopt a DevOps approach, simplify and accelerate continuous development, integration and deployment (CI/CD).

Experts en gestion financière du cloud-démarche FinOps- architecture microservices

They chose our digital know-how

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