Fallout 4 Downgrader

Tool for downgrading Fallout 4 to the pre-next-gen updates

GitHub Nexus Mods
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Why It Exists

After Fallout 4's next‑gen update, large portions of the ecosystem (F4SE plugins, Buffout, address library dependent mods) broke. This tool reverts the game back to the pre–next‑gen version so mod stacks remain usable while maintainers catch up.

Quick Start

  1. Download FO4Down.zip from Nexus or GitHub.
  2. Extract anywhere (does not need to be inside the game folder).
  3. Run one of: Downgrade By Patching Files.bat (fast) / Downgrade By Downloading Depots.bat (full).

Tip: FO4Down.exe will attempt patch first; if patching isn't possible it will proceed to depot download (Steam login / QR if required).

Patch vs Depot Download

  • Patching Files – Uses existing next‑gen executables; replaces only targeted binaries. Requires required plugins (F4SE, Address Library, Backported Archive2 Support System). Optional helper: Downgrade By Patch Files and Install Plugins.bat.
  • Downloading Depots – Retrieves the entire legacy build (longer). Replaces all game & data files. Leaves you with a clean pre–next‑gen state.
  • If you patch first then later run a depot downgrade, remove the backporter plugin DLL if you encounter early CTDs.
  • Version guard auto-corrects if Fallout4.exe ends up mismatched (e.g. 1.9.4 anomaly).

Arguments (CLI)

Usage: FO4Down.exe [options]
  -user|-username <steam user>
  -pass|-password <steam pass>
  -qr                 Login via QR
  -ck|-creation-kit   Downgrade Creation Kit too
  -all-languages      Download all languages
  -language <lang>    Specific language (default EN)
  -keep-depot         Keep depot files after completion
  -help               Show help

Current Status

Maintenance mode. No new feature expansion planned unless upstream structural changes mandate adaptation. Monitoring updates for breaking deltas.

Safety & Scope

Only touches files necessary for compatibility restoration – no telemetry, no extraneous modification. Users retain full control and can revert using backups.

FAQ (Condensed)

  • Needs .NET? Small zip requires .NET 8; large zip bundles runtime.
  • Where to extract? Anywhere – auto-detects install path.
  • Out of disk space? Move the whole folder; resume continues.
  • Credentials? Only used to authenticate ownership for depot download. Inspect source for verification.
  • QR login? Use the QR batch or -qr flag.
  • Different language? Use -language <code> or -all-languages.
  • Creation Kit? Use -ck or its batch; auto-detected if installed.
  • Prevent future updates? Set the appmanifest file to read-only after downgrading.
  • Crash after downgrade? Remove obsolete Creation Club or backporter DLL leftovers.

Disclaimer

Fallout® is a registered trademark of Bethesda Softworks. This tool is unaffiliated and provided as-is.