If something on the website isn't compatible with your setup, the site can serve you a different page. The browser's user agent is a short string of text that tells a website which OS and browser you're using. This requires spoofing your browser's user agent. To get those direct ISO file downloads on Windows, you'll need to make your web browser pretend you're using another operating system. If you access the website from another operating system - like macOS or Linux - you're sent to a page where you can directly download an ISO file instead. Microsoft's Media Creation Tool is only for Windows. How Do You Get a Windows 10 ISO Directly From Microsoft? Here's how to download Windows ISOs without the creation tool. Microsoft makes Windows 10 ISO images available to everyone through its download website, but if you're already using a Windows machine, it forces you to download the Media Creation Tool first.
