Minecraft Alpha is a very old, pre-1.0.0 development phase of Minecraft. Its development was headed by Markus Persson ("Notch") and spanned from June 2010 to December 3rd 2010, in a variety of greater or lesser levels of difference between versions. The most notable versions of Minecraft Alpha, perhaps, are Alpha 1.1.2_01 and Alpha 1.2.6.
The first two things a present-day Minecraft player might notice when playing this game are, in this order, a strongly different visual tone, and a highly-decreased array of features compared to newer versions. It's been more than 14 years, after all.
Some players having an introduction to Minecraft Alpha might be overwhelmed by just how spacious and spread-out the feature list is. There are far fewer "features" to engage with. In all of Alpha there are fewer than 94 blocks (many of which you wouldn't think about - or consider for building material - very much), and only about 11 mobs. The version doesn't throw at you a lot to do.
Yet, somehow, Minecraft Alpha, even in 2025, is weirdly fun. If you can get around the diminished armoury of toys and built-in goals, Minecraft Alpha is in spite of everything one of the most beautiful and absorbing things you can play. Alpha 1.1.2_01 is my Alpha version of primary choice. Even though the game has numerous flaws - which I can list, another time - Minecraft Alpha's visuals, balancing, progression, and terrain just come together and make something almost impossibly well-feeling. It blew up massively at the start of 2010 for a reason. I still remember...