Are planks good for climbing?

The real question would be if planks are good for your core.

Your core is very important for climbing as it is used in almost any climbing move, and can really help make you a better climber. It helps stabilize you, it can help keep you closer to the wall, and it can help you move in ways that without core strength would be very, very difficult.

So, core strength is very important for climbing, now the question is if planks are a good core exercise, or if it has little effect on the core.

Based on what can be found online, many people suggest doing planks instead of other exercises such as crunches due to less strain on the spine.
Planks work your back, shoulders, abs, legs and arms, all at the same time, while putting less strain on your spine, which is why many people recommend it.

Whether there are other exercises that are better for core strength than planks is another question, but based on what experts say and on research that can be found online, doing planks is a great exercise for core strength, which should translate to being a great exercise for climbing since climbing requires a strong core.