Before downloading Minecraft Alpha 1.2.7, make sure your computer meets the minimum system requirements:
Once created, you can go to the "Play" tab, select your new Alpha installation from the dropdown, and hit play. The launcher will automatically download the authentic, unmodified files from Mojang's servers. Minecraft Alpha 1.2.7 Download
You don't typically download this version manually. If you own the Bedrock Edition Before downloading Minecraft Alpha 1
If you want a standalone old launcher (not recommended for casual users), the MultiMC launcher can install Alpha versions safely using Mojang’s version metadata. But the official launcher is simpler. Before downloading Minecraft Alpha 1.2.7