Download and install Rufus, then:

This report outlines the current availability, official download methods, and support status for the Windows 8.1 64-bit ISO file.

Despite being superseded by Windows 10 (and later Windows 11), the Windows 8.1 64-bit ISO retains significant practical relevance. Its most prominent role today is as a lifeline for older hardware. Many PCs manufactured between 2012 and 2015, with processors like Intel’s 2nd or 3rd generation Core i-series, run Windows 10 poorly but operate with surprising snappiness on Windows 8.1. Furthermore, Windows 8.1 has a smaller disk footprint and lower background resource usage than Windows 10, making it ideal for low-spec laptops or repurposed thin clients. Another critical niche is software compatibility. Certain industrial, scientific, or legacy business applications—particularly those relying on older versions of .NET Framework or specific database drivers—may fail on Windows 10 or 11 but function flawlessly on Windows 8.1. For organizations with certified workflows, the ISO is an indispensable asset for maintaining legacy systems.

In the vast ecosystem of operating systems, few have occupied such a peculiar and controversial space as Windows 8.1. Released by Microsoft in October 2013 as a free update to the maligned Windows 8, it served as a crucial bridge between the radical, touch-centric vision of its predecessor and the more traditional, user-friendly approach of Windows 10. At the heart of deploying, reinstalling, or preserving this operating system lies a single, powerful file format: the ISO. An "ISO Windows 8.1 64-bit" is far more than a simple download; it is a complete, bootable, and archivable digital blueprint of an entire operating system, representing a specific moment in personal computing history and a continued practical solution for legacy hardware, software compatibility, and virtualization.

If you prefer to create a bootable DVD: