Almost every week, Mojang (the developers behind Minecraft) release a new snapshot of the game on their website. These snapshots are essentially previews of the new features that are going to be included in future versions of Minecraft.
To install a snapshot, all you are going to need is a local installed copy of Minecraft on your computer.
1. Download a copy of the snapshot from the Minecraft Versions website.
There you will find a link to download the Minecraft client and server JARs for the snapshots – download them.
2. Open the folder ‘bin’ in the Minecraft directory.
Replace the Minecraft JAR file in this folder with the snapshot JAR file you downloaded.
Remember: Back up your original minecraft JAR file so you can go back after you’re done with the snapshot. You can copy and rename your Minecraft JAR file to something else (example: minecraft_jar_backup.jar) so that you can reuse it once you are finished with the snapshot.
At this point the snapshot is now installed, although you will find that single player does not work because you need to add the minecraft_server Minecraft JAR files in the directory.
3. Go back to the root of the data directory Minecraft and create a new folder named ‘server’, if it does not already exist.
In this folder you need to place the minecraft_server JAR file that you downloaded with the snapshot.
4. Go ahead and open the Minecraft launcher and log in as usual.
If the snapshot has successfully installed, you should see a different version number at the bottom left of the window of Minecraft.
Uninstalling a Minecraft Snapshot
When you are finished with the snapshot, return to the Minecraft directory, navigate to the folder ‘bin’ and delete the Minecraft JAR file and replace it with the original file. Then go back to the root directory and remove the Minecraft server folder and all its contents.
It’s probably a good idea to create a new world or backup your current world before you play on snapshot because the changes made to the files may make it unplayable on the latest official release of the game.