How do I view campaign performance reports by device (desktop, tablet & smartphone)?

In self-serve go to ‘Analytics‘.

Choose ‘Action by Device Type‘ you will see the performance metrics broken down by device in a table.

For all campaigns (unless you choose a specific product from the drop down list) you will see the Computer Actions, Computer Clicks, Computer Action Rate, Tablet Actions, Tablet Clicks, Tablet Actions Rate, Mobile Actions, Mobile Clicks, Mobile Action Rate.

All these metrics can be put in ascending or descending order if you click on the table titles. Tip: use data to show performance on different devices and then edit creative features of the campaign for the device you are targeting.