# 30 leading Software Development companies in the Yvelines department

Tamtam tracks 56 Software Development companies headquartered in the Yvelines department. This list ranks the 30 largest by number of employees on LinkedIn, led by Dassault Systèmes, SELL and 4D. Their median headcount is 47. Half of them were founded in 2003 or later. The most common headquarters are Montigny-le-Bretonneux (5), Versailles (5) and Velizy-Villacoublay (3).

These software development companies in Yvelines include a large group, Dassault Systèmes, alongside many mid-sized firms. Their activities span a wide range of specialized software solutions, from product lifecycle management to business intelligence and mobile app development. Companies like SELL focus on optimizing sales strategies with cloud platforms, while 4D offers a low-code development platform. Médiane Système specializes in embedded AI and cybersecurity, and 6WIND provides cloud networking software.

A notable pattern among these companies is their geographical concentration. Several companies, including 4D, Médiane Système, and Siveco Group, are headquartered in Le Pecq and Montigny-le-Bretonneux. There is also a cluster in Versailles with companies such as SQI, COSIUM, and EURODECISION - Groupe DecideOm.

🇫🇷 Yvelines · 30 companies · Updated Nov 11, 2026

| # | Company | Industry | Headquarters | Employees | Founded |
|---|---|---|---|---|---|
| 1 | [Dassault Systèmes](https://www.tamtam.ai/c/dassault-systemes) (3ds.com)<br>Pioneering virtual worlds since 1981, this company offers a platform enabling customers across industries to collaborate, imagine, and create sustainable innovations for real-life impact. | Software Development | 🇫🇷 Velizy-Villacoublay | 27,414 |  |
| 2 | [SELL](https://www.tamtam.ai/c/sell) (sell-marketing.com)<br>A French independent company helps businesses master product information to optimize their sales strategy using the SELL BASE cloud platform | Software Development | 🇫🇷 Croissy-sur-Seine | 587 | 2006 |
| 3 | [4D](https://www.tamtam.ai/c/4d) (us.4d.com)<br>A full-stack hybrid Low-Code Development platform that enables quick creation and deployment of web, mobile, and desktop applications for businesses worldwide | Software Development | 🇫🇷 Le Pecq | 405 | 1984 |
| 4 | [Médiane Système](https://www.tamtam.ai/c/mediane-systeme) (medianesysteme.com)<br>Specializes in custom secure real-time operating systems, private 5G networks, embedded AI, cybersecurity, and industrial network solutions. | Software Development | 🇫🇷 Le Pecq | 213 | 1989 |
| 5 | [6WIND](https://www.tamtam.ai/c/6wind) (6wind.com)<br>Global leader providing ultra-high-performance cloud networking software, enabling telcos and businesses to build disaggregated software routers on standard servers, achieving carrier-grade throughput and efficiency. | Software Development | 🇫🇷 Montigny-le-Bretonneux | 110 | 2000 |
| 6 | [Siveco Group](https://www.tamtam.ai/c/siveco-group) (siveco.com)<br>A global leader in CMMS software, with over 37 years of experience in project management, serving clients in over 60 countries | Software Development | 🇫🇷 Montigny-le-Bretonneux | 107 | 1986 |
| 7 | [SQI](https://www.tamtam.ai/c/sqi) (sqi.fr)<br>Helps companies in project mode, especially in construction, public works, and technical trades, build tailored information systems and offers IT services and partnerships. | Software Development | 🇫🇷 Versailles | 106 | 1990 |
| 8 | [Avanteam](https://www.tamtam.ai/c/avanteam) (avanteam.fr)<br>A software editor specializing in BPM and ECM solutions, using innovative technologies like AI, serving over 500 customers in Europe | Software Development | 🇫🇷 Velizy-Villacoublay | 104 | 2003 |
| 9 | [4DConcept](https://www.tamtam.ai/c/4dconcept) (4dconcept.fr)<br>Specializing in content and editorial engineering, 4D CONCEPT provides tailored solutions for digital content production, publishing, archiving across various industries | Software Development | 🇫🇷 Montigny-le-Bretonneux | 74 | 1989 |
| 10 | [COSIUM](https://www.tamtam.ai/c/cosium) (cosium.com)<br>Cloud-based software and hardware solutions for healthcare industry, offering ICT outsourcing, Business Intelligence tools, and custom-designed electronics for optical retail and domiciliary care | Software Development | 🇫🇷 Versailles | 65 | 2003 |
| 11 | [Coptis](https://www.tamtam.ai/c/coptis) (coptis.com)<br>A company specializing in advanced technology solutions for Cosmetic R&D, offering software for product development, compliance management, and toxicology information | Software Development | 🇫🇷 Croissy-sur-Seine | 58 | 1999 |
| 12 | [NGHS](https://www.tamtam.ai/c/nghs) (nghs.fr)<br>Specializes in mobile app development for Android and iOS, creating Offline Dictionaries and Grid games apps with a total of 15 million installations | Software Development | 🇫🇷 Marly-le-Roi | 53 | 2011 |
| 13 | [EURODECISION - Groupe DecideOm](https://www.tamtam.ai/c/eurodecision-groupe-decideom) (eurodecision.com)<br>Specializing in business analytics, EURODECISION helps teams make optimal decisions by analyzing data and offering customized solutions using mathematical algorithms and AI | Software Development | 🇫🇷 Versailles | 50 | 1987 |
| 14 | [OSE Engineering](https://www.tamtam.ai/c/ose-engineering) (ose-engineering.fr)<br>Developing innovative software and technologies focused on improving work experiences through quality, customer-centric solutions and continuous innovation. | Software Development | 🇫🇷 Saint-Rémy-lès-Chevreuse | 49 | 2014 |
| 15 | [Pomelo-Paradigm](https://www.tamtam.ai/c/pomelo-paradigm) (pomelo-paradigm.com)<br>An innovative company designing collaborative applications with simple tools to enhance human productivity across all media platforms | Software Development | 🇫🇷 Versailles | 47 | 2013 |
| 16 | [Allshare](https://www.tamtam.ai/c/allshare-guyancourt) (allshare.fr)<br>Helps HR, C&B, and Finance teams align workforce with company strategy and build compensation policies to attract, retain, and engage employees. | Software Development | 🇫🇷 Guyancourt | 46 | 1992 |
| 17 | [PHOENIX FLEET EXPERT](https://www.tamtam.ai/c/phoenix-fleet-expert) (phoenix-fleetexpert.com)<br>PHOENIX FLEET EXPERT offers fleet management solutions including outsourcing, software, and shared management to optimize clients' vehicle fleets effectively | Software Development | 🇫🇷 Méré | 45 | 2011 |
| 18 | [InSitu](https://www.tamtam.ai/c/insitu) (transtechnology.fr)<br>A French company developing and selling user-friendly sales software for space design professionals, offering personalized solutions and attentive customer service | Software Development | 🇫🇷 Montigny-le-Bretonneux | 40 | 1995 |
| 19 | [Veryswing](https://www.tamtam.ai/c/veryswing) (veryswing.com)<br>French editor providing SaaS management software for IT services, consulting firms, design offices, and umbrella companies, ensuring high security and regulatory compliance. | Software Development | 🇫🇷 Versailles | 36 | 2012 |
| 20 | [MédiFirst](https://www.tamtam.ai/c/medifirst) (medifirst.com)<br>Dedicated to serving medical professionals in Assisted Reproduction (ART) and Genetics, the company provides an EMR system to streamline patient journeys and boost operational efficiency. | Software Development | 🇫🇷 Montigny-le-Bretonneux | 32 | 2002 |
| 21 | [MonEcho - logiciel médical](https://www.tamtam.ai/c/monecho-vidal-group) (monecho.com)<br>Provides an online software solution for ultrasound practitioners and hospitals, integrating with all ultrasound machines and ensuring data security and efficient workflow. | Software Development | 🇫🇷 Plaisir | 25 | 2009 |
| 22 | [EVOGEST LOGEST](https://www.tamtam.ai/c/evogest-logest) (evogest.fr)<br>EVOGEST is your partner for integrated ERP solutions and computer hardware in Orgeval, France, specializing in business management and IT equipment | Software Development | 🇫🇷 Orgeval | 24 | 2007 |
| 23 | [APSYS Business Partner \| Rydge Conseil](https://www.tamtam.ai/c/apsys-business-partner-rydge-conseil) (apsys.fr)<br>Integration of management software solutions for French SMEs, offering consulting, deployment, project management, and ongoing support services. | Software Development | 🇫🇷 Poissy | 21 | 1993 |
| 24 | [SUNERIS SOLUTION](https://www.tamtam.ai/c/suneris-solution) (suneris.com)<br>Develops, manufactures, and markets telecom software and hardware solutions for supervision, analysis, optimization, and security of telecommunication networks. | Software Development | 🇫🇷 Velizy-Villacoublay | 20 |  |
| 25 | [MAIDIS SAS](https://www.tamtam.ai/c/maidis-sas) (maidis.fr)<br>Development and marketing of comprehensive electronic health record software for medical and dental practices, hospitals, and health centers. | Software Development | 🇫🇷 Chatou | 19 | 2003 |
| 26 | [Gestimum](https://www.tamtam.ai/c/gestimum) (gestimum.com)<br>Manufacturer of user-friendly ERP software, Gestimum, tailored for 20-500 employee companies Constantly updates with new features and offers related services | Software Development | 🇫🇷 Rambouillet | 19 | 2004 |
| 27 | [KERLOG](https://www.tamtam.ai/c/kerlog) (kerlog.com)<br>Software publisher specializing in waste management for environmental and recycling industries, serving over 350 clients with 4,000+ users across France and overseas territories | Software Development | 🇫🇷 Le Pecq | 19 | 2003 |
| 28 | [ID Infos](https://www.tamtam.ai/c/id-infos)<br>A software integration expert since 1984, specializing in Sage and EBP, offering expert technical solutions with a personalized and human touch for clients | Software Development | 🇫🇷 Saint-Rémy-lès-Chevreuse | 18 | 1984 |
| 29 | [CASYOPE Services](https://www.tamtam.ai/c/casyope-services) (casyope.fr)<br>Specializes in digital transformation through monetary services, dematerialization, development, and personalized client support with skilled technicians and developers. | Software Development | 🇫🇷 Les Essarts-le-Roi | 18 | 2006 |
| 30 | [NET POINT](https://www.tamtam.ai/c/net-point) (netpoint.fr)<br>Aggregation of SaaS, IaaS, and PaaS solutions from multiple vendors through a cloud marketplace platform named Provicloud. | Software Development | 🇫🇷 Croissy-sur-Seine | 17 | 2011 |

## How this list is built

Every company on this list has a Tamtam company profile. The industry is the one the company gives on LinkedIn; categories such as SaaS or fintech are classified by Tamtam's AI from the company's website and LinkedIn page; and the headquarters city must match the company's own address. Companies are ranked by the number of employees on LinkedIn, and the list is refreshed every night. Classifications can be wrong, so treat the list as a starting point rather than an official ranking. Last updated Nov 11, 2026.

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Source: https://www.tamtam.ai/l/software-development-companies-yvelines