Dynamics 365 CE - Switch from Unified Interface to legacy webclient & vice-versa

Switch from Unified Interface to legacy webclient 

1. Click on setting icon.

2. Click on Advanced Security.

3. Navigate to Security -> Administration -> System Settings

4. Navigate general tab -> Use the new unified interface only section

5. Enable only the Unified interface = NO & click on OK

Switch from legacy webclient to Unified Interface

1. Navigate to Settings -> Administration -> System Settings

2. Navigate general tab -> Use the new unified interface only section

3. Enable only the Unified interface = YES & click on OK