Quick answer
What to do first
Keep a B41 world on legacy41, and a pre-42.20 B42.19 world on the retained 42.19 branch if you want to continue it. The official 42.20 release says 42.19 saves are incompatible with 42.20. For a fresh current game, use Stable 42.20.4. Back up first; a copied save is protection, not a format converter.
Check your game conditions
- Current Stable
- 42.20.4 Stable
- Play mode
- Singleplayer / Multiplayer
- Vanilla / Mods
- Vanilla baseline; mods may replace rules
- Sandbox / server settings
- Branch and save format, not a difficulty setting, determine compatibility; preserve the original world.
Match your save to a branch
| Existing world | Intended action | Branch / decision | Before proceeding |
|---|---|---|---|
| Build 41 | Continue the same world | Use legacy41 | Preserve the save and its compatible mods. |
| Build 42.19 | Continue the same world | Use the retained 42.19 branch | Do not open the only copy in 42.20. |
| Build 41 or 42.19 | Play current Stable content | Start a separate current world | Keep the old branch/save available if you want to return. |
| Current 42.20-series world | Continue after an update | Read that update's compatibility notes | Keep a pre-update backup; do not assume all future patches are compatible. |
| Multiplayer world | Keep the group together | Agree one compatible server/client branch | The host must preserve world data and the required mod set. |
Choose preservation or new content
Continuing an old world and seeing all current map changes are different goals. Keeping the old branch preserves its environment; starting a new Stable world avoids pretending the old map can be safely regenerated in place.
In Steam, open the game's Properties and the Game Versions & Betas section to select the retained branch named in the official instructions. This is a Steam branch path, not a promise that every storefront has an identical menu.
Treat mods and the server as part of the decision
The old world may rely on mods that do not support the new branch. Preserve the list and author versions with your backup. Disabling a content mod can itself change a save, so do not experiment on the only copy.
For multiplayer, the server owner should announce the target branch before anyone updates. If the group restarts, use a separate world/profile and confirm backups are available before abandoning the old session.
Version notes & limits
Branch choices follow the official 42.20 release instructions, checked September 4, 2026. Future patch or branch availability can change; recheck the official announcement before migrating.
Branch and restart decisions only; file-by-file backup and recovery are in the save guide. No unofficial conversion tool or future-compatibility promise.
Last verified means the linked documentation was reviewed, not that this guide was tested in-game. PZwiki is maintained by community contributors.
Version & sources
Sources & what may change
- Applies to
- 42.20.4 Stable; Singleplayer / Multiplayer; Vanilla baseline; mods may replace rules
- Last verified
- 2026-09-04
- When to check again
- A relevant Stable patch, changed world setting, mod update or correction to the cited instructions.