Project Zomboid Build Versions — Buildcode History & How to Check Yours
Every Project Zomboid Build 42 release with exact build numbers and dates: 42.20 stable, 42.21 unstable, how to check your buildcode and switch Steam branches.
FAQ
What is the latest stable Build 42 version?
How do I check my buildcode in Project Zomboid?
Can I go back to an older build after a save warning?
Current Status Official
As of this page’s last edit (2026-09-25):
| Branch | Build | Since | Official announcement |
|---|---|---|---|
| Stable | 42.20 (42.20.4) | 2026-07-29 | Build 42.20 Released |
| Unstable | 42.21 | 2026-09-23 | Re-population of the Dead: 42.21 Unstable |
The headline promise of the 42.20 stable release, in TIS’s own words: a heavily evolved Knox Country, deeper crafting and building, animals and husbandry, improved lighting, and expanded environmental storytelling — the culmination of the Build 42 features overview.
Build 42 Release Timeline Official
Milestones sourced directly from The Indie Stone’s news archive — no third-party dates:
| Date | Release | What mattered | Source |
|---|---|---|---|
| 2024-12-17 | Build 42 Unstable launch | First public B42 iteration after years of preview | Build 42 Unstable Out Now — official Steam announcement |
| 2026-03 | 42.15-era update wave | Game modes refresh (Apocalypse/Outbreak/Rising/Extinction), 6 new firearms | Some New Things |
| 2026-03-30 | 42.16 balancing pass | Daytime Sprinters in Extinction, Echo Creek removed as spawn, Tinkerer/Target Shooter traits | Balancing Time |
| 2026-07-24 | Stable plan announced | Date lock for the big glow-up | Build 42 Stable Plans |
| 2026-07-27 | Pre-release feature wrap | Map/town glow-up recap | 42.20: The Big Glow Up |
| 2026-07-29 | 42.20 — Build 42 goes stable | Full Knox Country rework, animals, crafting depth; both branches aligned at 42.20.4 | 42.20 Released |
| 2026-09-23 | 42.21 Unstable | Zombie re-population system — the next test cycle begins | Re-population of the Dead |
How to Check Your Buildcode Official
- Main menu — the version string prints on launch; this is the number mod pages and bug reports expect you to quote.
- Steam branch picker — Library → right-click Project Zomboid → Properties → Betas; the dropdown shows which branch (stable or a named build channel like
42.19) you are opted into. - Why it matters — mod compatibility breaks across major iterations. B41 mods do not carry into B42 unchanged, and even B42 patch lines shift trait and loot data, which is why every guide on this wiki carries its own version badge.
Save Compatibility Warnings Official
From the official 42.20 release post: existing saves on Unstable 42.19 are not compatible with 42.20 — TIS’s own remedy is selecting the matching old beta channel in Steam properties if you want to finish a run there. Treat any “carry your save across versions” claim elsewhere with suspicion: when The Indie Stone says a migration is unsupported, it is.
Version-by-version patch notes are maintained upstream; for per-system guides on what each update changed in play, start with the Build 42 overview and the returning-player migration guide, and see the dedicated server guide for pinning a server to a branch.
Related Articles
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Build 42 Update Overview — Everything New in the Big One
Build 42.20 — Knox County doubled, crafting reworked, livestock added, lighting overhaul. Complete overview verified July 2026.
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Build 41 → 42 Migration Guide — Saves, Branches, and What You Need to Know
Build 41 saves don't transfer. Three options: fresh on 42.20, legacy41 beta, or 42.19 beta. Step-by-step Steam instructions.
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Should You Return to Build 42? — A Returning Player's Survival Guide
Played Build 41 for hundreds of hours? Build 42 is the biggest update ever. Here's exactly what changed and why you should come back.
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