The simplest way to add Wi-Fi to a desktop PC is by adding a USB wireless adapter. These devices plug into any available USB port, and once the drivers are installed, they allow the PC to connect wirelessly to any network. Internal PCI cards with wireless adapters are also available.
While a USB wireless adapter is the easiest solution, it may not be the best one. The bandwidth available for the Wi-Fi connection is limited by the speed of the USB port, and if other devices are connected that transfer large amounts of data, such as a portable hard drive, overall speeds may decrease. In addition, the reception of USB adapters can vary substantially, and it may require reorienting the computer to get the strongest signal.
PCI cards typically offer better performance, and most feature one or more antennas for improved reception. However, these require a free PCI slot on the motherboard, and the user must open the case to install the expansion card. Some PCs have small form factor motherboards that can make this installation a tricky process.
Both USB and PCI network adapters must be compatible with the wireless standard of the network in order to connect. As of 2015, 802.11ac is the newest wireless standard, but 802.11n and 802.11g networks are still commonplace. While some routers allow connections from older hardware, a Wi-Fi network generally runs faster and more smoothly if all the connected devices use the most recent protocols.