Currently both the Classic Mode and the Unified Interface (UI) of Microsoft Dynamics 365 can be used however the Classic Mode is going to be deprecated by Microsoft soon. If you are still using the Classic mode but you would like to take a quick peak at the new UI, there is a quick and easy way to make the switch without the need to fiddle with settings which I will show you below.
If you have come across issues with functionality on the new UI and need to check the Classic mode again, you can use this method as well.
To Access the Unified Interface:
In the URL, type forceUCI=1 after main.aspx?
To Access the Classic Mode:
In the URL, type forceCLASSIC=1 after main.aspx?
So, if you are still using the Classic Mode, give the new Unified Interface a try. It’s simple as making a change to the URL.
The following image shows the display of the Unified Interface