The short answer
Usually, after a check. Might hold something you care about. Look inside before removing it.
What is it?
This folder holds extra Swift compilers installed from swift.org (release, snapshot or development builds), each as an .xctoolchain bundle, and is also where the swiftly version manager places toolchains on macOS. The Swift compiler that comes with Xcode lives inside Xcode itself, not here. Each toolchain typically takes one to a few gigabytes.
Extra Swift compilers installed from swift.org (1-3 GB each). Keep the ones your projects select; others can be downloaded again.
What happens if you delete it?
A removed toolchain can be downloaded again from swift.org (or with swiftly), but nothing reinstalls it automatically. Projects or scripts that select it, through Xcode › Toolchains or the TOOLCHAINS environment variable, fail until you reinstall it.
How to remove it properly
If you installed it with swiftly, use swiftly uninstall <version> so swiftly’s records stay in sync. Otherwise quit Xcode and move the .xctoolchain bundles you no longer need to the Trash from ~/Library/Developer/Toolchains; a toolchain installed for all users lives in /Library/Developer/Toolchains and needs an administrator password.
Quit the app that uses it, then move it to the Trash. Empty the Trash when you’re sure.
Before you delete it
Check whether a project, CI script or Xcode’s Toolchains menu still points to a snapshot before removing it.
How MoreRoom helps
MoreRoom recognises this item and labels it “Review first”: it shows what’s inside, its size and last use, so you can decide. Nothing is removed without your say, and everything goes to the Trash first, with Undo.
Frequently asked questions
Can I delete Swift toolchains in ~/Library/Developer/Toolchains?
Usually, after a check. Might hold something you care about. Look inside before removing it. A removed toolchain can be downloaded again from swift.org (or with swiftly), but nothing reinstalls it automatically. Projects or scripts that select it, through Xcode › Toolchains or the TOOLCHAINS environment variable, fail until you reinstall it.
Will Swift toolchains come back after I delete it?
Yes. A removed toolchain can be downloaded again from swift.org (or with swiftly), but nothing reinstalls it automatically. Projects or scripts that select it, through Xcode › Toolchains or the TOOLCHAINS environment variable, fail until you reinstall it.
How do I remove Swift toolchains properly?
If you installed it with swiftly, use swiftly uninstall <version> so swiftly’s records stay in sync. Otherwise quit Xcode and move the .xctoolchain bundles you no longer need to the Trash from ~/Library/Developer/Toolchains; a toolchain installed for all users lives in /Library/Developer/Toolchains and needs an administrator password.