Project Zomboid Patch Tracker — Build 42.20.x and 42.21 Dates and Changes

Current Status — 42.21 Is Stable Official

Build 42.21 has been the stable release since 28 September 2026, five days after it landed on Unstable. The Indie Stone’s own reasoning is unusually plain: “In this instance the community did not report any major issues, so the ‘Go’ button is being pressed… today.”

This page is the patch record we can actually stand behind. It replaced an earlier version of itself: two patch tables that disagreed with each other on the same build numbers, and quotes attributed to The Indie Stone that do not appear in any announcement. Both tables were wrong on dates as well as contents, so nothing from them survives below. For the branch-by-branch view, see the buildcode history.

The Verified Patch Record Official

Dates are taken from the announcement itself, not from a third-party summary.

Two things in that table are easy to get wrong and worth repeating: 42.20.1 and 42.20.2 both shipped on 5 August 2026, and there is no 42.20.5. The next release after 42.20.4 was 42.21.

What 42.21 Actually Changed Official

1. Zombies no longer duplicate or vanish when you cross a chunk boundary. The post describes it as the same class of bug hitting both singleplayer and multiplayer, “particularly obvious in larger zombie population games”. TIS is explicit that it is not finished: “there are still some instances of this which we have on our radar and will be fixed in our next update.” If you run population high, this is the fix that mattered.
2. XXL trees stopped blocking your view while driving. New cutaway behaviour for players in vehicles, trees no longer hide the houses and furniture they overhang, and overall transparency was raised. TIS calls it “a work in progress and will receive more love in future” — so expect more here, not less. Driving specifics are in the vehicles guide.
3. loadstring and loadstream are back. Covered below, because it is the one change with consequences for your mod list.

The loadstring Round-Trip — Why Modders Care Official

The two Lua methods were removed in 42.20.4 (26 August) to close a security vulnerability, then re-enabled in 42.21 after TIS finished investigating and concluded the risk was acceptable — with an apology aimed at modders and server admins.

Read together, the two announcements give you a practical rule: a mod that broke in late August was probably not abandoned, it was caught by the removal. If you maintain or subscribe to Lua-heavy mods, check whether they were updated for 42.20.4 and again for 42.21 rather than assuming obsolescence. Branch management itself is in the migration guide.

Saves, Branches, and the One Real Wipe

The 42.20.x hotfixes all carry the same line: the update “should not break saves”, with the standard ask to reproduce bugs on a fresh save with no mods before reporting. The exception that bites people is the 42.19 → 42.20 boundary — added map content made those saves incompatible, which is why TIS froze a 42.19 beta branch, and legacy41 for Build 41 saves. All three options, with the exact Steam clicks, are in the migration guide.

How to Stay Updated

We update this page when a new announcement lands, not when a rumour does. Every fact on it traces to a row in our internal fact table, and the deletions above are recorded there too.