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Simulator runtime

Quick answer

A simulator runtime is the OS version image that an Xcode simulator boots, such as iOS 18.4.

A simulator runtime is the OS version image that an Xcode simulator boots, such as iOS 18.4.

Why it matters

Downloading one at job time costs several minutes per run. Pinning to a runtime already on the image removes that cost entirely.

Your next build could be twice as fast, at half the price

Start free. Migrating away is the same one line, and we publish that diff too.