Which file controls the Killing Floor 2 menu background?

MenuBG.BIK in killingfloor2\KFGame\Movies. It is a Bink video that plays behind the main menu.

Do I need to back up anything?

Yes. Copy or rename the current MenuBG.BIK before adding the old one, so you can switch back later.

Will a game update undo this?

A file verification or an update that touches the movie can restore the new background. Repeat the swap if that happens.

Binds & Console

How to Get the Old Killing Floor 2 Menu Background Back

Each big Killing Floor 2 update can change the animated background behind the main menu. If you preferred the older look, the swap is a simple file replacement: the menu background is just a Bink video, and the short Steam guide behind this page explains how to put the old one back.

What you need

The old menu video saved as a .bik file. The guide author hosted it on a file-sharing link; any copy of the original MenuBG.BIK works.
Access to your Killing Floor 2 install folder.

Steps

Download the old BIK file.
Open the game files: in Steam, right-click Killing Floor 2, choose Properties, Local Files, Browse. You can also go straight to killingfloor2\KFGame\Movies.
Back up the current MenuBG.BIK by copying it somewhere safe or renaming it (for example MenuBG_new.BIK).
Put the downloaded file into the folder and make sure it is named exactly MenuBG.BIK.
Start the game. The old background should play behind the main menu.

Going back

Delete the old file and restore your backup, or run "Verify integrity of game files" in Steam to download the current version again.

FAQ

Which file controls the Killing Floor 2 menu background?: MenuBG.BIK in killingfloor2\KFGame\Movies. It is a Bink video that plays behind the main menu.
Do I need to back up anything?: Yes. Copy or rename the current MenuBG.BIK before adding the old one, so you can switch back later.
Will a game update undo this?: A file verification or an update that touches the movie can restore the new background. Repeat the swap if that happens.