Install a theme

A theme is a folder with an index.html, called a template. Templates live under <profile>\webview-ui\, one folder per template, and the active one fills the main window. How a page is found explains the full lookup.

Create a template and copy the theme into it

1. Open File → Preferences → Display → WebView2 UI.
2. Press Manage... and choose Create.... Enter a name made of letters, digits, - and _, then confirm. foobar2000 creates <profile>\webview-ui\<name>\ with a placeholder index.html and selects the new template in the Template box.
3. Press Open... to open the template folder in File Explorer.
4. Copy the theme's files into it, replacing the placeholder index.html. For a project built with a bundler, copy the contents of its output folder (for Vite, dist), not the folder itself.
5. Press Apply. The main window, and every panel that follows the global template, reloads with the theme.

Apply refuses a template whose folder has no index.html, or an empty one.

Switch between installed templates

Pick another entry in the Template box and press Apply. Creating, renaming and deleting templates are file operations that happen at once and are not undone by Cancel; the active template and any template a loaded panel uses cannot be renamed or deleted.

Use a template in one panel only

A panel can load its own template instead of the global one: see Put a page in a panel.

When the development server is on

While Use development server (HMR hot reload) is ticked on the Developer page, pages load from the server URL and a template change does not reload them. Untick it and press Apply to see the installed template. See Debug a theme with the development server.