I have some seeds from some old worlds I want to see again, is there a mod that allows the ability to create alpha worlds with seeds or would it be possible to make a world blank but with the seed so that when the world is loaded it generates the world with seed using the generation type of that version?

3 Answers

Here is how you can make a world with a custom seed in Minecraft Alpha, before you could change the seed in-game

1. Start Minecraft Alpha by changing the version in the Minecraft Launcher
2. Create any world, and save and exit Minecraft
3. Use NBTedit to open level.dat found in the saves/ folder of .minecraft
4. Open Data/RandomSeed and change this to your seed you want
5. Delete all the chunk files
6. Open the world in Minecraft again

I'm nearly 6 years late, but someone made a fabric mod which adds a seed selector into alpha 1.2.2a. Here is a zip you can import into MultiMC to use fabric mods in 1.2.2a.

I found a mod that let's you use old alpha seeds if you're still looking for this. There's no need to do this whole world update stuff just download this mod for 1.12.2. I know it says it's a server plugin, but I can 100% guarantee that it will work like any other mod, just download forge for minecraft 1.12.2 and drag this mod into the mod folder, when you're creating a world, select "world type: alpha 1.1.2_01" and then you're done. This mod doesn't generate villages or anything like that, but if you're using mods such as recurrent complex, rouge-like dungeons etc. it will generate those structures. Anyway Here's the link.