Changelog for Thunderbird 86

The following WebExtension API changes were introduced in Thunderbird 86.

api theme

The theme API allows for customization of Thunderbird’s visual elements.

api theme

• property theme_experiment — A theme experiment allows modifying the user interface of Thunderbird beyond what is currently possible using the built-in color, image and property keys of theme.ThemeType. These experiments are a precursor to proposing new theme features for inclusion in Thunderbird. Experimentation is done by mapping internal CSS color, image and property variables to new theme keys and using them in theme.ThemeType and by loading additional style sheets to add new CSS variables, extending the theme-able areas of Thunderbird. Can be used in static and dynamic themes.