What number of threads does Kotlin's Dispatchers.IO dispatcher use by default?

By default, Kotlin Coroutine Dispatchers.IO uses a thread pool whose size is the maximum of two values:

• 64
• Number of CPU cores * 64

For example, if you have 8 cores, the pool size will be 512 threads (8 * 64), but not less than 64.

This is designed for efficient handling of a large number of blocking I/O operations, allowing many coroutines to run in parallel without blocking the main threads.

You can get the number of threads like this:

println((Dispatchers.IO as ExecutorCoroutineDispatcher).executor.maximumPoolSize)

However, keep in mind that this is an internal behavior and may change in different library versions.