Parsec is PC software that allows for desktop sharing across the internet. That could be one person using a low-powered laptop to connect to their high-powered home desktop computer. It could be two (or more) people coming together to play a game session, head to head or sharing controls.
The guest’s attached controls, including a USB gamepad, can appear on the host machine, as if they were there in person. Gamepad access works via Parsec’s Virtual USB Gamepad function. This must be enabled on the host machine via Settings > Host > Parsec Virtual USB Gamepads. You can choose from virtual Xbox 360, Dualshock and Dualsense simulation. Try Xbox 360 to start with.
Note, Parsec must be running on both machines, with accounts set up, friended, and a session active.
Once the guest presses a button on their controller, it should quickly come to life. A small gamepad icon should turn green whilst pressing buttons. The guest gamepad should appear in the Windows joy.cpl utility (type it in the Windows search bar). Alternatively, try the on-line Joypad.ai gamepad tester utility.
Some games may need to be remapped to suit the particular game. Steam has in-built remapping. You may find a remapping tool such as JoyToKey or ReWASD helpful.
Parsec can be used as a form of co-pilot, whereby one player can help another. This can be useful for a player struggling with a particularly tricky part of a game. Or just for the pure fun of it.
For those looking to push the system a little further, the following may be of interest:
Advanced
A rather complex method of using Parsec to have a computer remotely control a Nintendo Switch, using a Titan adapter and Elgato Game Capture device is detailed here: Nintendo Switch Parsec control.
Troubleshooting
Controller not working? Guest machines must have the Parsec window active. Kicking a user off, then asking them to re-join can help. They must press a button to bring their virtual controller to life.
Blocked from play? Some games will block the likes of Parsec and ReWASD out of cheating concerns. Most web-based and emulated games should work.
Co-pilot struggles? If two players wish to share the same gamepad controls to play as a single player, but can’t, because the game sees two controllers and starts a local two-player game, see this Guide for using ReWASD for a potential way around it.