Connecting an external microphone to a 13-inch MacBook Pro 2016 running macOS motonery

There are different types of 3.5mm plugs.

If your microphone cable has a plug with two rings, then it won't work directly (but may with an adapter).

Old pc had separate audio outputs and inputs of the 3.5mm variety, and the plugs were identical, with two rings.

Each mac since at least a decade ago has a single audio port that works both as input and output.

This requires a three-ringed 3.5mm jack to work.

You can read more about it here. Note that if you have a pair of headphones with mic, such as those used with smartphones, they will work.

What Do the Rings on a Headphone Jack Actually Do? We ...https://www.gearpatrol.com › Tech › Audio

I forgot to add: you can get a cheap Y-cable adapter to make it work. It has a male three-ring 3.5mm plug on one side and two female plugs on the other. Just plug your mic into the correct end of the adapter and plug the adapter to your mac.

You will need some adapter. But:

That little Y cable that I showed you should cost what... $4? Not very expensive. And you can connect the mic and headphones to it.

Mind you, this is not the same as a "splitter" cable that lets one attach two pairs of headphones (that would be even cheaper, but it's no use for a mic).

I think that change must have happened around 2012 or so.

Older macs had separate ports for audio input and output.

AFAICR, all the "Retina" macs have only one audio port, that can serve as both input and output.

Like this one: