> ## Documentation Index
> Fetch the complete documentation index at: https://docs.summerengine.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Keep a world running between sessions
> Give players a place they come back to: a base, a farm or a realm that is saved, sleeps while nobody plays, and wakes up just as they left it.
Most matches end and are gone. A **persistent World** is a place players come
back to, such as a shared base, a farm or a realm. Your game's server saves it
while people play. When nobody is playing, Summer can let the World sleep, and
the next time someone joins, it wakes up and restores from its last save.
## Games like this
A world your friends keep building in for months.
A small group's world that's still there next weekend.
A shared farm that keeps its crops and buildings.
If players should find the world the way they left it, this is the page for
you. If each match starts fresh, use
[matchmaking](/build/matchmaking) on its own.
## What your players get
* **The world as they left it.** Walls they built, chests they filled and crops
they planted are all still there.
* **Their own Worlds, one tap away.** Players find the Worlds they've played
under **My Worlds** in Summer Games, and your game can offer a "Return to my
World" button.
* **A warning before planned restarts.** When a World is about to restart or
sleep for maintenance, your game can tell players in advance, and the World
saves before it stops.
* **Worlds that survive updates.** Publishing a new version of your game
doesn't touch existing private Worlds: they keep their saves and the version
they started on. New Worlds use your newest version.
## What to save where
A World save holds what belongs to the **place**. What belongs to a **player**,
such as their level or the coins in their pocket, goes in
[player progress](/build/player-progress), so it follows them to every World.
Your game decides what goes in a save, and the save is always one consistent
moment. If a player moves an item from a chest into their inventory, the chest
and the inventory are saved together.
## Pick your setup
### A private World for a group
Each group gets its own World that only its players return to, like a Realm
or a co-op farm. Players come back to it from **My Worlds** or from your
game's menu, and a sleeping World wakes up and restores before they're let in.
In my Summer project, turn my World into a persistent World that players come
back to. Use the Summer `summer-world-saves` skill; if you don't have it
installed, find it in the Summer library.
* Save \[WHAT BELONGS TO THE PLACE, for example "everything players build and
the contents of chests"] regularly while people play.
* When the World starts, restore it from its last save before anyone joins.
* Remember each player's World so the menu can offer "Return to my World".
* Keep each player's own progress out of the World save; use the
`summer-player-data` skill for that.
Read my project first and list what you'd save before you change anything.
Then test it with Local Play and tell me what I can only check once the game
is hosted.
### Shared Worlds anyone can join
Players who search for a game join an existing World that has a free seat,
waking it up if it's asleep. Summer starts a new World only when none has
room. Good for public servers that grow a community over time.
In my Summer project, let players join shared persistent Worlds: a player
who presses Play joins an existing World with a free seat, and a new World
starts only when none has room. Use the Summer `summer-world-saves` and
`summer-matchmaking` skills; if you don't have them installed, find them in
the Summer library. The queue should place players in existing Worlds first
(`open_world_first`).
* Each World holds up to \[NUMBER] players.
* Save \[WHAT BELONGS TO THE PLACE] regularly, and restore it before anyone
joins.
Read my project first and explain how a player gets from my menu into a
shared World before you change anything.
### Warn players before a planned restart
Before Summer restarts a World or puts it to sleep for maintenance, your game
gets notice in advance. Use it to warn players and wrap up anything in
progress. Gameplay then pauses for a final save, and the World comes back
exactly as it was.
In my Summer project, warn players before my persistent World restarts or
sleeps, and save it before it stops. Use the Summer `summer-world-saves`
skill; if you don't have it installed, find it in the Summer library.
* When a planned stop is announced, show players a countdown, such as
"Server restarts in 5 minutes", and hide it again if the stop is cancelled.
* Don't start long activities, like a boss fight, close to the stop.
* Make the final save when Summer asks for it.
Keep the regular saves too: an unexpected crash doesn't send a warning.
## Not sure which fits?
Read my Summer project and help me plan persistent Worlds for it. Use the
Summer `summer-world-saves` and `summer-player-data` skills; if you don't
have them installed, find them in the Summer library. Don't change any files
yet.
Tell me:
1. whether my game wants private Worlds for a group or shared Worlds anyone
can join;
2. what belongs in the World save and what belongs in each player's progress;
3. how players find their way back to a World;
4. anything my design needs that persistent Worlds don't cover yet, and how
we can build around it.
## Testing it on your machine
Local Play runs your persistent World with saves kept in memory. Every run
starts with an empty World, saving works and returns a confirmation, and
nothing is kept after the run ends. That's enough to check that your World
saves while people play and restores before anyone joins. Coming back to the
same World after a real restart happens in the hosted game.
***
Does this not help you? [Reach out on Discord!](https://discord.gg/summerengine)
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