Earlier today Nintendo issued a new firmware update for the Switch which brings video recording, data transfer and some other goodies to the table.
However, it's not just the main console which got an update today - the Joy-Con controllers have also been issued with a firmware refresh.
To update them you simply go to Settings > Controllers and Sensors > Update Controllers. Each Joy-Con will be updated separately, and if you have more than one set you'll want to connect them in pairs to make sure they're on the latest firmware.
What this controller update actually does is anyone's guess, but let us know if you notice any differences.
Thanks to Ryan Millar for the tip!