Apple has confirmed that it is planning a software update that will add multi-monitor support to the 14-inch M3 MacBook Pro models. The M3 MacBook Air model launched today can support up to two 5K external monitors when used in closed mode, while the 14-inch MacBook Pro using the same M3 chip currently does not have this feature.
Since both machines use the same M3 chip, it's unclear why the MacBook Air has this feature and the MacBook Pro doesn't, but Apple is planning to rectify the problem. In the near future, a software update will add an option for the 14-inch M3 MacBook Pro to drive two external monitors when the lid is closed.
Both M3MacBook Air and M3MacBookPro support an external monitor, with a resolution of up to 6K and a frequency of 60Hz when the monitor is turned on; after the update, the M3MacBook can also support two 5K external monitors with a resolution of up to 60Hz. This is equivalent to StudioDisplay, so users can expect to run two Apple 5K monitors in closed-lid mode.
The higher-end M3 Pro and M3 Max MacBook Pro models can already drive multiple monitors, so this change only applies to the 14-inch MacBook Pro with the M3 chip. This model replaces the previous generation 13-inch MacBook Pro, which Apple has now canceled.