The best part of Minecraft is the endless supply of amazing worlds to build in and explore. The unique world generator can create literally billions of combinations of biomes in Minecraft: desert, tundra, teeming swamps, impenetrable jungles, surface lava lakes, underground chasms, and the rare Mushroom Biome. Minecraft also randomly generates special features like mine shafts, Strongholds, and NPC villages in the Minecraft world.
All of these biomes and features start with strings of code called world seeds. The terrain generator update in Beta version 1.8 (the Adventure Update) means older seeds are no longer compatible with newer versions of Minecraft, but there are still plenty of Minecraft world seeds online to choose from.
Map Seed Compatability
Because of the updated terrain generator, new Minecraft World Seeds and world seeds created after the prerelease (Beta) versions are not compatible with older versions of Minecraft. If you are running an older version of Minecraft, you won’t be able to use new map seeds. Likewise, world seeds from older Minecraft versions and Beta versions don’t generate the same maps in the current version of Minecraft. To make sure the seeds you use copy the original maps and spawn points, make sure you are running the most current, updated version of Minecraft.
Players have posted thousands of cool Minecraft seeds on the Minecraft Forum and seed libraries like Minecraft-Seeds.net. Many seed libraries and forums allow you to search for Minecraft world seeds by game version. Make sure you choose seeds that are compatible with your version of Minecraft!
Setting Map Seeds
You can manually input a seed when you create a new world by clicking “More World Options.” Type the word/phrase or numbers of the seed you want to use or copy and paste the seed into the “Seed for the World Generator” text box. Click “Done” to return to the Create New World screen.
Using a seed from the Forum, YouTube, etc. means you’ll be playing on the exact same map as the original. If you prefer to play in a random Minecraft world, you can type in random words or numbers or leave the world generator field blank, which makes the world generator use the time and date the map is created as a base for the seed. According to the Minecraft Wiki, leaving the field blank gives you access to 18 quintillion possible map seeds.
If you input a word or phrase as the world seed, it restricts the world generator to (only!) 4 billion possible maps due to the way the generator interprets letters vs. numbers. However, seemingly random words and phrases have generated some of the best Minecraft seeds available. It is sort of a game among members of the Minecraft online community to test out the wackiest word combos for world seeds and show off the amazing maps that result. For example, the word seeds “worstseedever” and “i dont care.”