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Hello :wave:. I've been thinking about the challenges of maintaining backwards compatibility in libraries and wondered at what points would you use the Deprecation Levels? I've been using `WARNING` by default and then removing the signatures on a major version bump. But why, for example, shouldn't I just mark everything as `HIDDEN` by default?

What approaches do you take?

• Major version `n`: `WARNING`
• Major version `n+1` : `ERROR`
• Major version `n+2`: remove symbol

You can use `HIDDEN` if you know the symbol is used a lot and you want to maintain binary compatibility. kotlinx.coroutines is doing it <https://github.com/Kotlin/kotlinx.coroutines/blob/feea16dc641eef7be884f1d2b8f9b454820bd5b4/kotlinx-coroutines-core/common/src/NonCancellable.kt#L117|here> for an example.

I would use hidden directly (without warn-error cycle) if there is an overload that is source compatible. Like if you add a new parameter with a default value to a function, you can keep the original function and mark it as hidden.

See also <https://youtu.be/cCgXtpVPO-o|https://youtu.be/cCgXtpVPO-o>

Thanks everyone :pray:. And thanks for the video Márton. That's exactly what I was looking for. Some great advice there.