If you want to play older Minecraft versions safely and legally, use the official Minecraft launcher (it includes older versions once you own the game) or visit Mojang/Microsoft support pages for guidance on legacy versions.
Minecraft Alpha v1.2.6 is a historical version of the Java Edition originally released on December 3, 2010. If you are looking for a download link, , which provides verified versions of historical releases. How to Download Officially Minecraft 1.2.6 Alpha Download LINK
: Provides detailed technical metadata and official piston-data.mojang.com download links for the Client .jar Internet Archive If you want to play older Minecraft versions