Xcode Simulator: how to remove older unneeded devices?

In Xcode 6+ you can simply go to Menu > Window > Devices > Simulators and delete a simulator you don't need.

October 2020 update

As was mentioned, you can use xcrun to do a few things:

• xcrun simctl list devices or xcrun simctl list --json to list all simulators
• xcrun simctl delete <device udid> to delete specific device
• xcrun simctl delete unavailable to remove old devices for runtimes that are no longer supported

More things you can do with xcrun (see code snippet)

- `xcrun simctl boot <device udid>` to launch (multiple) simulators
- `xcrun simctl io booted recordVideo — type=mp4 ./test.mp4` to record simulator video
- `xcrun simctl io booted screenshot ./screen.png` to make screenshot of simulator
- `xcrun simctl openurl booted https://google.com` to open URL in simulator
- `xcrun simctl addmedia booted ./test.mp4` to upload photo or video file (for photos app)
- `xcrun simctl get_app_container booted <your apps bundle identifier>` to find the app container (where identifier is like *com.bundle.identifier*)
- `xcrun simctl help` to explore **more** commands

Original Answer

September 2017, Xcode 9

Runtimes

You will find them here:

/Library/Developer/CoreSimulator/Profiles/Runtimes

Devices

To delete devices go here:

~/Library/Developer/CoreSimulator/Devices

Much easier to delete them use Xcode: Xcode->Window->Devices and Simulators

Helping Xcode "forget" about runtimes and prevent from re-installing them - delete .dmg file(s) here:

~/Library/Caches/com.apple.dt.Xcode/Downloads

I hope it will help someone 🙂

Did you try to just delete the 4.3 SDK from within the Xcode Package?

/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs

please also delete the corresponding .dmg file in

~/Library/Caches/com.apple.dt.Xcode/Downloads

to prevent Xcode from re-installing the same package again.

for XCode >= 6 see @praveen-matanam 's answer

In Xcode 6 and above, you can find and delete the simulators from the path /Library/Developer/CoreSimulator/Profiles/Runtimes. Restart Xcode in order to take effect (may not be needed).