How many threads are used by default in Dispatchers.IO when working with Kotlin Coroutines?

By default, Dispatchers.IO uses a thread pool whose size is the minimum of two values: 64 and the number of available CPU cores multiplied by 2. This is done to efficiently perform a large number of blocking I/O operations without excessive thread creation.

That is, if you have 8 cores, the pool size will be min(64, 8 * 2) = 16 threads.