Direct answer

The checker runs entirely in your browser and does not upload save files, Workshop lists, logs, or account data. It combines the official Build 41, 42.19, and 42.20.4 branch boundaries with lightweight checks for duplicate Workshop IDs, version markers, removed Lua methods, file mismatches, and multiplayer isolation steps.

Do this first

  1. Choose the branch you intend to run and the version that created the save.
  2. Select solo, hosted co-op, or dedicated server.
  3. Paste one Workshop ID or URL per line when mods are involved.
  4. Paste only the first relevant log error if you have one.
  5. Follow the linked guide and test on a disposable world before restoring the full preset.

Private browser tool · Build 42.20.4

Check your branch, mods, and next step

This is a conservative compatibility triage tool. It reads only the text you paste into this page; nothing is uploaded.

Recommended path · selected 42.20.4

Start on the current Stable line

  • Create a new world on Stable 42.20.4 and record the exact version before adding mods.
  • Use Stable 42.20.4 as the comparison target and test on a disposable world first.
Open the matching guide

What the checker can decide

It can identify the correct preservation branch for Build 41 or 42.19, recommend a backup before same-line updates, flag common 42.20.4 Lua and file-mismatch symptoms, find duplicate Workshop IDs, and choose between save, mod, version-mismatch, joining-game, and server guides.

  • Branch and save-line mismatch
  • Removed loadstring or loadstream calls
  • Duplicate or missing Workshop IDs
  • Client/server version markers in a pasted log
  • A conservative vanilla-first test order

What it cannot prove

A text-only browser check cannot execute a mod, inspect your save, query the Steam Workshop, or guarantee that a community item works in every world. Treat a clean result as permission to isolate and test—not as a compatibility certificate.

  • No automatic Workshop API verdict
  • No save editing or repair
  • No server connection test
  • No mod files retained or uploaded

Privacy and evidence

Inputs stay in the current browser session. The tool requests no file upload, Steam account, server address, or personal information. For a support report, keep the exact game/server version, first relevant error, operating system, and the smallest failing mod list.

FAQ

Quick answers

Does the tool upload my save, mod list, or log?

No. All fields are read in the browser and nothing is sent to a server.

Can it guarantee a mod is compatible?

No. It flags common version and log clues, then routes you through a reversible vanilla-first test.

Should I paste every line of console.txt?

No. Paste the first relevant error or a short excerpt; a focused clue is easier to interpret and keeps the tool usable.

Evidence log

Sources checked

Official sources establish universal facts; forum and specialist sources are used for symptoms, vocabulary, and cross-checking.

OfficialProject Zomboid Build 42.20 Released

Official Stable status, legacy41 instructions, and the explicit Build 41/42.19 save boundaries.

Official42.20.4 Stable Security Hotfix

Official 26 August security hotfix for Stable 42.20.4, beta 42.19.2, and legacy41 41.78.21, including removal of loadstring and loadstream.

OfficialFeatures Overview: Build 42.20

Official overview of the expanded map, new towns, basements, animals, crafting, occupations, traits, mod manager, and multiplayer UI.

Specialist guideProject Zomboid Mods Guide

Specialist cross-check for current mod-manager, Workshop, load-order, and multiplayer terminology.

Specialist guidePZ Mod Compatibility Checker · Build 42 Edition

Open-source desktop checker used as a competitor and capability benchmark; its scan results are not treated as a universal compatibility authority.