What is IIS (Internet Information Services)?
IIS (Internet Information Services) is the web server software built into Microsoft Windows Server. It is the default choice for hosting websites and applications built with Microsoft technologies, including ASP.NET, ASP.NET Core, and Classic ASP. IIS is included free with Windows Server licensing.
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When a company runs a web application built with C# and ASP.NET, or uses Microsoft SQL Server as its database, IIS is typically the web server handling incoming requests. IIS integrates tightly with the Windows operating system and the .NET framework, making it the natural choice for Windows-based web deployments.
IIS handles HTTPS via Windows certificates, supports WebSocket connections, includes a management console for configuration, and has a module system for extending functionality. Application pools in IIS allow different applications to run in isolated worker processes, improving stability and security.
For standard websites and applications built with PHP, Python, Node.js, or other non-Microsoft technologies, Apache and Nginx running on Linux are the standard choice. IIS is specifically for Windows-based applications. Choosing Windows hosting when you do not need it adds cost (Windows Server licensing) without benefit.
Windows hosting with IIS is available from providers like Winhost, Arvixe, and major cloud providers (AWS, Azure, Google Cloud all support Windows virtual machines). Microsoft Azure is particularly popular for .NET applications because of its tight integration with Microsoft's development tools and services.
Common questions
Do I need IIS for my website?
Only if your application uses ASP.NET, Classic ASP, or Microsoft SQL Server. WordPress, PHP sites, Node.js apps, and Python applications run on Linux servers with Apache or Nginx, not IIS.
Is IIS free?
IIS itself is free and included with Windows Server. However, Windows Server requires a paid license, which is why Windows hosting costs more than Linux hosting. IIS cannot run on Linux.
Is Apache better than IIS?
For Linux-hosted PHP and open-source applications, Apache is the better fit. For Windows-based .NET applications, IIS is the appropriate choice. They serve different ecosystems rather than competing directly for the same workloads.