Run WebView2 UI next to another interface

Background mode keeps a WebView2 UI window available while Default UI or Columns UI is the main interface, for example as a lyrics or artwork companion window, or to show visualizations while you manage playlists in Default UI.

Turn it on

1. Open File → Preferences → Display → WebView2 UI → Window, tick Background mode: keep the WebView running while another user interface is active and press Apply. The label is translated when the component language is Chinese.
2. Choose the other interface under File → Preferences → Display → Default User Interface.
3. Restart foobar2000. Background mode takes effect after a restart.
4. Show the window with View → WebView2 UI → Show/Hide Window.

The window loads the global template, like the main window does. Tick Restore background window visibility on startup on the same page to bring it back as you left it when foobar2000 starts.

When the menu entry reads "Preferences..."

Without a WebView2 UI window, for example when the other interface is active and background mode is off, the menu entry under View → WebView2 UI reads Preferences... and opens the WebView2 UI preferences page instead.

Keep the page working while it is hidden

When the window is minimized, hidden to the tray or the session is locked, the page's document.visibilityState becomes hidden: requestAnimationFrame stops and timers are heavily throttled. Update the page from events (fb2k.on(...) or fb.on(...)) rather than polling loops, so it is correct again when it comes back. When you automate the player over CDP or MCP, the keep-alive option in the MCP setup guide keeps the page active in these states.