Custom Software Development for SMEs and Startups

We build web applications, apps and AI integrations for businesses in the Netherlands. You talk directly to the developer who builds it, with no account managers in between.

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Just launched

Websites and apps we delivered recently. Click through to the live version.

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01 / HeuminLive
Heumin, AI SaaS · iOS & Android
AI SaaS · iOS & Android
02 / SanimaxLive
Sanimax, Website · Lead generation
Website · Lead generation
03 / ABN VloerverwarmingLive
ABN Vloerverwarming, Website · Price calculator
Website · Price calculator
ABN Vloerverwarming redesign
1 week
Sanimax load time
±1 sec
Languages in Heumin
11
Heumin, one codebase
iOS + Android

What our clients say

“Our new website is really fast, with load times of 1 second, and everything responds intuitively. Exactly what we had in mind.”

Sanimax

Website · Haarlem
sanimax.nl
“A complete solution with AI integration, from app to platform. We are very happy with the end result.”

Heumin

AI app · iOS, Android & web
heumin.com
“Within a week our website was completely redesigned and all funnels were correctly integrated. We are very happy with the result.”

ABN Vloerverwarming

Website & funnels · Haarlem
abnvloerverwarming.nl
AI

AI agents and automation

We connect language models to your existing systems so recurring work like quotes, tickets and data entry largely runs by itself. Where it matters, a colleague approves it first.

agent · quote assistantrunning
  1. $ New quote request via website
  2. 01Read email and attachments
  3. 02Found customer in CRM
  4. 03Calculated area: 42 m², milled
  5. 04Estimated price from price table
  6. 05Drafted quote (PDF)
  7. 06Waiting for approval from a colleague
More about AI solutions
  1. 01

    AI agents

    An agent carries out a task end to end, for example drafting a quote from an email. We build the agent, the integrations and the approval step.

  2. 02

    Workflow automation

    Connections between your CRM, ERP, email and spreadsheets, with AI where it's needed and plain code where that's enough.

  3. 03

    LLM integrations

    Claude, GPT or an open-source model inside your own software, with logging, limits and a clear view of the costs.

  4. 04

    Knowledge base and RAG

    An assistant that answers from your own documents and cites the source.

  5. 05

    MCP servers

    Integrations that let AI assistants work safely with your internal systems, with only the permissions they need.

  6. 06

    Chatbots

    For customer service or internal use, multilingual, and handing over to a colleague when the bot doesn't know.

Services

What we build

From an internal tool to a complete platform

  1. 01

    Custom web application development

    Internal tools, customer portals and SaaS platforms. We build them so you can add features later without starting over.

  2. 02

    Backend & API development

    The servers, databases and APIs behind your applications. We build REST and GraphQL APIs and connect them to your existing systems.

  3. 03

    Custom business software

    Software for processes no standard package fits. We build it around the way your business works.

  4. 04

    Cloud & infrastructure

    Hosting on Azure, AWS or Google Cloud. We set up the environment, automate deployments and keep an eye on costs.

  5. 05

    AI solutions & agents

    AI agents, automation and LLM integrations that run inside your existing processes and software.

Something else in mind?

Tell us what you want to build. After one conversation you'll know whether and how we can build it.

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Approach

How we build custom software

Short lines, well-known technology and clear agreements on time and money

What we often help with

  • Standard software doesn't fit your process

  • Old systems hold you back

  • A bad experience with a software agency

  • No technical knowledge in-house

SEMSIT

  • Direct contact with the developer

    You talk to the developer who builds your project. There is no account manager in between. Technical questions get a direct answer.

  • Built around your way of working

    The software follows your business processes. You don't have to adapt the way you work to fit a package.

  • Well-known, stable technology

    We build with React, Next.js, Node.js, .NET and PostgreSQL. This technology is widely used, so your software is easy to extend later.

  • Clear planning and pricing

    You get a plan and a price up front. During the project you hear how things stand. We discuss extra costs before we incur them.

Why SEMSIT
01

No account managers

You talk directly to the developer. They understand your technical question and answer it themselves.

02

Honest about what's possible

We say up front what we will do and stick to it. If something isn't feasible, we tell you.

03

Right before fast

We'd rather deliver a little later and have it work properly. Your software should last for years.

04

After delivery too

After delivery we stay available for maintenance, updates and new features.

Process

How a project with SEMSIT works

From the first conversation to delivery, in four steps

  1. 01

    Free introductory call

    You tell us what you need and what you have already tried. There is no obligation.

  2. 02

    Analysis and quote

    We turn your question into a concrete proposal, with approach, planning and costs.

  3. 03

    Building

    We build in short steps and regularly show you what's finished. You can adjust course along the way.

  4. 04

    Delivery and support

    We test the software, write documentation and show your team how it works. After that we stay available for support.

Who we build for

  • SMEs in the Netherlands

    Businesses that are stuck with standard software and want a web application that fits the way they work.

  • Startups

    Startups that want an MVP built or want to extend an existing product. Without the cost of a large agency.

  • Businesses with outdated software

    Organisations that want to replace old systems or automate manual processes.

Need custom software built

Book a free call with our developers. We look at your situation and discuss what's possible for your web application or business software. There is no obligation.

Book a free call