Cable bought on long spools to install permanently is usually solid, while patch cables are usually stranded. Most of the time, you'll end up buying pre-terminated stranded cable, and all the cable you terminate yourself will be solid.

Does it even matter if the cable is solid or stranded? When you put on that new RJ45 connector the cables go into the connector with the insulation on.

I tried and failed three times. Gave up, and pulled solid cable. TIL that some rj45 connectors have multiple teeth, and interlock.

Stranded as in each wire being made up of smaller wires.

https://en.wikipedia.org/wiki/Wire#Stranded

These are typical in pre-capped wires. While they allow more flexibility of the wire, their ends are hard (if not impossible) to change.

I've never seen stranded wire in an ethernet cable, but I see it's a thing. I occasionally turn my male-male ethernet into male-female with a keystone block and never see stranded.

I dabble in electronics and I eliminate stranded wire whenever I find it. Some people love it but I find it really inconvenient.

Solid Ethernet cabling should generally only be used on permanent building cable that never move. Stranded should be used on patch cables and cables that get moved around. Beyond being more difficult to handle, regular movement will break solid copper, often leading to intermittent connectivity.

Stranded ones are very common in patch cables.

patch cable wire is stranded. the clip here is meant for use on patch cables and has nothing to do with keystones