Live preview of themes is provided. At least one invoked activity is detected in a web application. At least one candidate theme is obtained. The at least one candidate theme includes at least one style element for the web application. On the client device, display of a theme preview interface is caused. The theme preview interface includes at least one live preview. Each live preview corresponds to one of the at least one invoked activity and one of the at least one candidate theme. In response to selection of a selected theme, a current theme of web application is switched to the selected theme.