iOS detect if user is on an iPad

This is part of UIDevice as of iOS 3.2, e.g.:

[UIDevice currentDevice].userInterfaceIdiom == UIUserInterfaceIdiomPad

There are quite a few ways to check if a device is an iPad. This is my favorite way to check whether the device is in fact an iPad:

if ( UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad )
{
    return YES; /* Device is iPad */
}

The way I use it

#define IDIOM    UI_USER_INTERFACE_IDIOM()
#define IPAD     UIUserInterfaceIdiomPad

if ( IDIOM == IPAD ) {
    /* do something specifically for iPad. */
} else {
    /* do something specifically for iPhone or iPod touch. */
}   

Other Examples

if ( [(NSString*)[UIDevice currentDevice].model hasPrefix:@"iPad"] ) {
    return YES; /* Device is iPad */
}

#define IPAD     (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad)
if ( IPAD ) 
     return YES;

For a Swift solution, see this answer: https://stackoverflow.com/a/27517536/2057171

In Swift you can use the following equalities to determine the kind of device on Universal apps:

UIDevice.current.userInterfaceIdiom == .phone
// or
UIDevice.current.userInterfaceIdiom == .pad

Usage would then be something like:

if UIDevice.current.userInterfaceIdiom == .pad {
    // Available Idioms - .pad, .phone, .tv, .carPlay, .unspecified
    // Implement your logic here
}