ViaVersion / ViaVersion

Allows of newer clients to connect to older server versions for Minecraft servers.

ViaVersion / ViaFabricPlus

Minecraft Fabric mod that allows you to join every Minecraft server version (Classic, Alpha, Beta, Release, April Fools, Bedrock)

ViaVersion / ViaProxy

Standalone proxy which allows players to join EVERY Minecraft server version (Classic, Alpha, Beta, Release, Bedrock)

ViaVersion / ViaBackwards

Allows older clients to connect to newer server versions for Minecraft servers.