Saving, worlds and seeds | Mantlenaut Wiki

Worlds and seeds

Each world is one planet. When you start one, the game gives it a seed, a short name such as amber-4821. The seed decides what the planet looks like, so the same seed always gives the same world. A world also has a name of its own, made from the seed, such as Emberhold, which you can change later.

New world: in the Survival or Free Roam panel on the main menu, leave the seed blank for a brand new planet, or type a seed to visit a planet you know.
In the address: the seed goes into the address, so reloading the page brings you back to the same planet.
Sharing a planet: send the seed to a friend, and they can start a world with it. Your changes stay yours, unless you share the world itself as a file (see below).
Earth-size or small: the world-size choice sets whether planets are true to life (Earth size, where you choose one of four starting regions) or small enough to walk round.

The pause menu (Esc) shows the seed of the world you are in, and has a New world button. That button saves this world first, then starts a fresh one, on the seed you give or on a new one.

When the game saves

Every minute while you play, the world saves itself.
When you pause, the world is saved before the menu opens.
When you leave for the main menu, to another world, or to close the game, it is saved first.
On demand: the Worlds tab has a Save now button, which tells you whether it worked.

Each save is written whole, so a crash or a closed tab leaves your last good save in place. The game also keeps a backup copy from the start of each visit, which is used if a save will not load.

What is kept

A save keeps your changes to the land, your bag and your gear, the crates and machines you built, your crops, the Codex, your standing with the villages, your jobs, the animals you have tamed, and the things lying on the ground. Wild creatures and villagers are not saved: they come back by themselves when you return. A boss that was mid-fight starts again the next time you meet it.

The Worlds tab

Open the pause menu (Esc) and choose Worlds. It lists the worlds kept in this browser, the last one played first, and for each one its mode, seed, time played and how many blocks you have changed.

What you can do	How
Play a world	Click Play on its row. The world you are in is saved first.
Rename the world you are in	Type a new name in This world and leave the box. Names are up to 32 letters, numbers, spaces, apostrophes and dashes.
Export a world	Click Export. You get a `.mantlenaut` file to keep or send to a friend.
Import a world	Click Import a world file, or drop a `.mantlenaut` file onto the game.
Delete a world	Click Delete, then click again to confirm. Deleting cannot be undone.
Start a new world	Type a seed (or leave it empty for a surprise) and click New world.

Worlds are kept in this browser on this device. If you want the same world on another device, use the cloud saves (see Cloud saves and accounts), or export it and import it there.

Private windows and full storage

Some browsers keep nothing for a game: a private window, or a browser with site storage turned off. The Worlds tab says so. In that case each visit starts a new world, and nothing is kept. The game also asks the browser to keep its storage for good the first time it saves, so it is not cleared when space runs low.

Tips

Export a world before a big change, or before you try a new mode. The file is a copy you can always import back.
A friend's world is theirs: when you join one, your own world is saved and waits for you, and you find it again on the Worlds tab.

For what the different modes mean for your world, see Game modes.

← Back to the wiki · Last updated 25 October 2026. Mantlenaut is in alpha, so things change.