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A coroutine still runs on some thread. A dispatcher decides which thread or pool it uses, and that choice matters on each platform.

Use Dispatchers.Default for CPU-heavy work like parsing or sorting. It exists on Android and iOS, so shared code can rely on it.

Dispatchers.Main runs on the platform UI thread. It is available in common code, but only update screens from here.

Watch out: Dispatchers.IO exists on the JVM and Android but not in plain common code on every target. Do not assume it is everywhere.

For portable shared logic, prefer Default and Main. They are guaranteed across the targets KMP commonly supports.

You move work between threads using withContext. Compute on Default, then hop to Main to publish the result, all in one function.

A dispatcher is just a CoroutineContext element. You can pass one in, which makes shared code easy to configure and test.

Passing the dispatcher in lets tests swap a deterministic one. Hard-coding it makes shared async logic harder to test. 🧪

On iOS these dispatchers map onto the right native queues automatically. Your shared code does not care about GCD details.

Because the dispatcher names are common, the same line schedules work correctly on Android and iOS. No platform branches in your logic. ✨

Rule of thumb: Default for computation, Main for UI updates, and inject anything IO-like so it stays portable. 🎯

Pick the dispatcher choice that is safest for shared KMP code.

You learned to pick dispatchers wisely: Default for computation, Main for UI, and inject IO-style ones since they are not on every target. 🎉