Mirroring a display to an external monitor and obtaining information on it under OS X

You should then see a copy of the information displayed on the laptop's builtin monitor also displayed on the external monitor.

On a MacBook Pro laptop, you can find information on the external monitor connected by a DisplayPort connection, such as model number, resolution, and even serial number by clicking on the Apple icon in the upper, left-hand corner of the window and selecting About This Mac, then clicking on the More Info button, then System Report. In the window that appears, scroll down to Graphics/Displays under Hardware. Click on Graphics/Displays to select information for that hardware item. Beneath Color LCD you should find another entry at the same level of indentation for the external monitor, which for the example below is an HP Compaq LA2405wg monitor with a resolution of 1920x1200.

You can also get the information from a command line interface (CLI) using the Terminal program found in Applications/Utilities by opening that program and using the system_profiler command. E.g., system_profiler | more. Hit the space bar until you get to the Graphics/Displays section where you will see information similar to the following:

Graphics/Displays:

    NVIDIA GeForce 9400M:

      Chipset Model: NVIDIA GeForce 9400M
      Type: GPU
      Bus: PCI
      VRAM (Total): 256 MB
      Vendor: NVIDIA (0x10de)
      Device ID: 0x0863
      Revision ID: 0x00b1
      ROM Revision: 3448
      gMux Version: 1.8.8
      Displays:
        Color LCD:
          Display Type: LCD
          Resolution: 1440 x 900
          Pixel Depth: 32-Bit Color (ARGB8888)
          Mirror: On
          Mirror Status: Hardware Mirror
          Online: Yes
          Built-In: Yes
        LA2405:
          Resolution: 1920 x 1200
          Pixel Depth: 32-Bit Color (ARGB8888)
          Display Serial Number: CN420702GW  
          Main Display: Yes
          Mirror: On
          Mirror Status: Master Mirror
          Online: Yes
          Rotation: Supported
          Connection Type: DisplayPort

As with the About This Mac method, I can see the model for the external monitor identified as LA2405 with a resolution of 1920 x 1200 pixels. The connection type is identified as DisplayPort.

You can also generate an Extensible Markup Language (XML) report containing just the information from the Graphics/Display section of the information using the command below:

The format for generating information just for specific hardware for the system is system_profiler [-xml] [dataType1 ... dataTypeN]. You can see a list of the available data types using the command

system_profiler 
-listDataTypes

$ system_profiler -listDataTypes
Available Datatypes:
SPParallelATADataType
SPUniversalAccessDataType
SPApplicationsDataType
SPAudioDataType
SPBluetoothDataType
SPCameraDataType
SPCardReaderDataType
SPComponentDataType
SPDeveloperToolsDataType
SPDiagnosticsDataType
SPDiscBurningDataType
SPEthernetDataType
SPExtensionsDataType
SPFibreChannelDataType
SPFireWireDataType
SPFirewallDataType
SPFontsDataType
SPFrameworksDataType
SPDisplaysDataType
SPHardwareDataType
SPHardwareRAIDDataType
SPInstallHistoryDataType
SPNetworkLocationDataType
SPLogsDataType
SPManagedClientDataType
SPMemoryDataType
SPModemDataType
SPNetworkDataType
SPPCIDataType
SPParallelSCSIDataType
SPPowerDataType
SPPrefPaneDataType
SPPrintersSoftwareDataType
SPPrintersDataType
SPConfigurationProfileDataType
SPSASDataType
SPSerialATADataType
SPSPIDataType
SPSoftwareDataType
SPStartupItemDataType
SPStorageDataType
SPSyncServicesDataType
SPThunderboltDataType
SPUSBDataType
SPNetworkVolumeDataType
SPWWANDataType
SPAirPortDataType