Windows 8.1 ISO Overview
Windows 8.1 ISO is the official Microsoft installation image for the final release of the Windows 8 line, including the Update 1 cumulative refresh from April 2014. The Windows 8.1 offline installer is downloaded as a ~3.5 GB ISO file from Microsoft's software download page and used to create a bootable USB drive or DVD for clean installation. Windows 8.1 reached End of Mainstream Support in January 2018 and End of Extended Support on January 10, 2023 — Microsoft no longer issues security updates. The OS still works on most hardware released between 2012 and 2018 and is occasionally needed by users restoring an older PC, virtualizing a legacy environment for testing, or maintaining systems running Windows 8.1-only line-of-business applications. The Windows 8.1 ISO requires a valid Windows 8.1 product key for activation. Microsoft no longer sells Windows 8.1 keys directly — keys must be retrieved from the original purchase, the COA sticker on a pre-installed laptop, or via Microsoft's volume licensing portal for organizational customers. To install: download the Windows 8.1 ISO from Microsoft, write it to an 8 GB USB drive using Rufus or the Media Creation Tool, boot from USB, and follow the setup wizard. For most users on supported hardware, upgrading to Windows 10 or 11 is strongly recommended — Windows 8.1 will not receive future security patches.