Internet Information Server is Windows-based software that runs websites
Internet Information Server (IIS) is web server software made by Microsoft. It takes requests from browsers — when someone types your domain name or clicks a link — and sends back the web pages, images, and files that make up your website. IIS runs on Windows Server operating systems, which means it lives on a physical computer (or virtual one) that stays on and connected to the internet all the time.
If you have ever used a web hosting provider, you may have chosen between "Windows hosting" and "Linux hosting" without knowing what that choice actually meant. IIS is the Windows option. The Linux equivalent is usually Apache or Nginx. Both do the same job — they listen for browser requests and deliver your website — but they work differently under the hood and support different programming languages and tools.
Most websites you visit run on Apache or Nginx because Linux hosting is cheaper and more common. But IIS powers a significant number of websites, especially those built with Microsoft technologies like ASP.NET, Microsoft SQL Server databases, or SharePoint. If your website uses any of those tools, IIS is likely the right choice.
Key Takeaways
- IIS is Microsoft's web server software that runs on Windows Server and delivers web pages to browsers when people visit your site.
- You typically encounter IIS when choosing between Windows hosting and Linux hosting from a web hosting provider.
- IIS works best with Microsoft technologies like ASP.NET, C#, and SQL Server databases, though it can run other types of websites too.
- IIS requires more expensive hosting than Linux-based servers, but offers tight integration with Microsoft development tools if that is what your team uses.
- Your hosting provider manages IIS installation and updates, so you do not need to install or configure it yourself unless you run your own server.
How IIS receives and answers browser requests
When someone visits your website, their browser sends a request to your web server asking for a specific page or file. IIS receives that request, figures out which file the browser is asking for, and sends it back. If the request is for a static HTML page, IIS just reads the file from disk and sends it. If the request is for a dynamic page — one that changes based on user input or a database query — IIS runs the code that generates that page and sends the result.
IIS listens on port 80 (for regular HTTP traffic) and port 443 (for encrypted HTTPS traffic). You do not need to know these port numbers to use a website, but they matter if you are setting up your own server or troubleshooting why a site is not reachable. Your hosting provider handles port configuration automatically.
IIS can also serve multiple websites from a single server by using something called host headers. This means one physical computer running IIS can power ten different domain names, each with its own website. The server looks at which domain name the browser requested and serves the correct website accordingly.
IIS and Microsoft technologies work together
IIS was built by Microsoft specifically to run Microsoft's own web development tools. If you build a website using ASP.NET (Microsoft's framework for building dynamic websites), IIS is the natural home for it. ASP.NET code runs inside IIS, which means the two are tightly integrated — IIS knows how to execute ASP.NET code, pass data to it, and handle errors.
The same is true for websites that use SQL Server (Microsoft's database software). IIS can connect directly to SQL Server, retrieve data, and display it on web pages. This integration is seamless because both products come from the same company and are designed to work together.
If you are building a website with PHP, Python, or Node.js instead, IIS can still run those languages, but it is not the natural fit. Linux hosting with Apache or Nginx is more common for those languages because they were developed in open-source communities where Linux is the standard platform. You can run them on IIS, but you are swimming against the current — the tools, documentation, and community support all point toward Linux.
Windows hosting costs more than Linux hosting
When you shop for web hosting, you will see that Windows hosting plans cost more than Linux hosting plans for the same amount of storage and bandwidth. This is because Windows Server licenses cost money, and hosting providers pass that cost to customers. Linux is free, so Linux hosting providers have lower costs to pass along.
The price difference varies by provider and plan, but expect to pay roughly 20 to 50 percent more for Windows hosting. If your website does not require Microsoft technologies, that extra cost is wasted money. If your website does require them — because you are using ASP.NET or SQL Server — then Windows hosting is the only option, and the cost is necessary.
Some hosting providers offer shared hosting (where your website shares a server with many others) or dedicated hosting (where you rent an entire server). IIS is available in both models. Shared hosting is cheaper but means your site shares resources with strangers. Dedicated hosting is more expensive but gives you the whole server to yourself.
Your hosting provider manages IIS, not you
If you use a web hosting company, you do not install or configure IIS yourself. The hosting provider installs it on their servers, keeps it updated, and handles the technical details. You just upload your website files and it works. This is true whether you use a simple file manager in your hosting control panel or more advanced deployment tools.
If you run your own server — which is rare for small websites but common in large organizations — then you do manage IIS yourself. You would install Windows Server, install IIS, configure it to serve your websites, set up security certificates for HTTPS, and handle updates. This requires technical knowledge and is a significant responsibility.
Most people never need to think about IIS directly. You choose Windows hosting or Linux hosting when you sign up with a hosting provider, and the provider handles everything else. The choice matters because it determines what programming languages and tools you can use, but the day-to-day operation is invisible.
IIS security and maintenance
Like any software, IIS has security vulnerabilities that Microsoft discovers and fixes over time. Hosting providers apply these security updates regularly, usually without you noticing. If you run your own server, you are responsible for applying updates yourself, which means checking for them regularly and testing them before deploying to production.
IIS also has configuration options that affect security. For example, you can restrict which file types IIS will serve, which IP addresses can access your site, and what permissions different users have. A hosting provider typically handles these settings for you based on industry best practices. If you run your own server, you need to understand these settings or hire someone who does.
One common security issue is leaving unnecessary features enabled. IIS comes with many optional modules and features that you may not need. Disabling the ones you do not use reduces the attack surface — the number of ways someone could potentially break in. Again, hosting providers usually do this for you.
When to choose Windows hosting with IIS
Choose Windows hosting if you are building a website with ASP.NET, ASP.NET Core, or C#. These languages are Microsoft technologies and run best on IIS. If your website needs to connect to a SQL Server database, Windows hosting is the natural choice. If your organization already uses Microsoft tools and your developers are familiar with them, Windows hosting keeps everything in the same ecosystem.
If you are building a website with PHP, Python, Ruby, or Node.js, Linux hosting is usually cheaper and more straightforward. These languages were developed in open-source communities and run on Linux by default. You can run them on Windows hosting, but you are paying extra for a platform that is not optimized for them.
If you are unsure what technology your website uses, ask your developer or the person who built it. They can tell you whether Windows or Linux hosting is the right fit. If you are building a new website and have not chosen a technology yet, consider your team's skills and the long-term cost of hosting.
Frequently Asked Questions
Is IIS the same as a web host?
No. IIS is the software that runs on a web host's server. A web host is the company that owns the server and rents space on it to you. IIS is one piece of the infrastructure that makes the web host work.
Can I run a website on IIS without paying for Windows hosting?
Only if you own and operate your own server, which requires buying hardware, an internet connection, and technical expertise. For most people and businesses, paying a hosting provider for Windows hosting is simpler and more reliable than running your own server.
Do I need to know how IIS works to have a website?
No. Your hosting provider handles IIS completely. You just upload your website files and it works. Understanding IIS helps if you are troubleshooting problems or making advanced configuration changes, but it is not necessary for basic website operation.
What is the difference between IIS and Apache?
IIS is Microsoft's web server software for Windows. Apache is the most common web server for Linux. Both do the same job — they deliver web pages to browsers — but they run on different operating systems and support different programming languages natively.
Can IIS run on Linux?
No. IIS only runs on Windows Server. If you want to run Microsoft technologies on Linux, you can use ASP.NET Core, which is Microsoft's newer framework designed to run on Linux, but it uses a different web server like Kestrel or Nginx instead of IIS.