Java quick answer: Open Multiplayer, add a server, and enter unstablesmp.net.
- Open Minecraft Java Edition.
- Click Multiplayer.
- Click Add Server.
- Enter unstablesmp.net as the server address.
- Join Unstable SMP.
Do not add a Java port unless Minecraft asks for one. The public Java address should be entered as unstablesmp.net.
Check the saved entry
The server name is just a label; use Unstable SMP. The address field should contain only unstablesmp.net, without https://, a path, or the Bedrock port. Saving the entry lets you reuse it from Multiplayer.
Before changing your installation
The checked Java status label is 26.2. A status label is not a guarantee that every older or newer client is accepted. Check current compatibility announcements if Minecraft reports an outdated client or server.
Use your legitimate Minecraft account. If authentication fails, close the game, check that the official launcher is signed into the intended account, and retry. Do not share your password or account tokens with anyone offering to fix a connection.
For the standard Java interface, see Mojang’s server joining guide.