What is visitor mode?

Visitor mode is meant to be used on non-modded vanilla Minecraft servers.
If you want to show your server to public without fear of them interacting with world, all you have to do is set default gamemode to adventure.

What this data pack does:

It basically sets entity to adventure player's head to block it from interacting with things like buttons, levers, or killing mobs. It also sets few buffs to the player so he does not have to worry about hunger or for its life.
The pack also prevents griefing mobs (creepers/ghasts) from attacking the player so no holes in ground and builds.

What this data pack lacks:

So far I have discovered few issues I am adressing on GitLab:

• players can stand on pressure plates and activate them
• players can sometimes interact with world when server lags

How to use it?

Just install and enable as any other data pack. If you don't know how to do it, read Minecraft wiki or my GitLab page. After that set default gamemode to adventure and disable gamemode force (force gamemode means every player would be switched to adventure after login).