How to Dynamically adjust the UI of the Salesforce Visualforce Page?

Hi Saurabh,

You can use $User.UITheme and $User.UIThemeDisplayed global variable to find the current user experience.
These global merge fields identify the Salesforce look and feel a user sees on a given Web page.
The difference between the two variables is that $User.UITheme returns the look and feel the user is supposed to see, while$User.UIThemeDisplayed returns the look and feel the user actually sees. For example, a user may have the preference and permissions to see the Lightning Experience look and feel, but if they are using a browser that doesn’t support that look and feel, for example, older versions of Internet Explorer, $User.UIThemeDisplayed returns a different value.