devicetype 1 means Mobile/Tablet - General
Generic mobile value from OpenRTB 2.0 for a phone or tablet when the seller cannot tell which.
When to send it
Value 1 is the original mobile entry from OpenRTB 2.0, when the list had only three rows. When OpenRTB 2.2 split mobile into 4 (Phone) and 5 (Tablet), it kept 1 and told bidders to accept it as meaning either. A seller should put 1 in Device.devicetype only when it really cannot distinguish the two, for example a mobile web request whose user agent does not reveal the form factor.
Buyers treat 1 as a blended mobile signal. Campaigns that target phones only, or that bid differently on tablet screens, have to fall back on screen dimensions in Device.w and Device.h or on their own user agent parsing. It is most often confused with 4 and 5: an app SDK that knows it runs on a phone and still sends 1 gives up pricing precision for nothing.
Example
{
"device": {
"devicetype": 1
}
}Fields that carry it
Other values in device types
The device types list page explains the whole list and its common mistakes.