The short answer
Usually, after a check. Might hold something you care about. Look inside before removing it.
What is it?
Build-tools are the command-line programs the Android build uses to package and sign apps (aapt2, d8, apksigner, zipalign and others), installed one folder per version under ~/Library/Android/sdk/build-tools. Each version is a few hundred megabytes at most, but they pile up over the years.
Older build-tools. The two newest are kept; Gradle downloads a missing version when a project needs it.
What happens if you delete it?
If a project needs a version you removed, the Android Gradle plugin downloads it on the next build, or you can reinstall it from the SDK Manager.
How to remove it properly
In Android Studio, open Settings › Languages & Frameworks › Android SDK › SDK Tools, tick Show Package Details and untick old versions; or run sdkmanager --uninstall "build-tools;<version>" in Terminal (permanent).
Use the tool’s official command: sdkmanager --uninstall "<package>"
- MoreRoom keeps the newest 2 and suggests the older ones.
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.
When the tool is installed, MoreRoom runs its official command for you (sdkmanager --uninstall "<package>") instead of deleting files — and tells you that this step can’t be undone.
Frequently asked questions
Can I delete old Android SDK build-tools versions?
Usually, after a check. Might hold something you care about. Look inside before removing it. If a project needs a version you removed, the Android Gradle plugin downloads it on the next build, or you can reinstall it from the SDK Manager.
Will Android build-tools versions come back after I delete it?
Yes. If a project needs a version you removed, the Android Gradle plugin downloads it on the next build, or you can reinstall it from the SDK Manager.
How do I remove Android build-tools versions properly?
In Android Studio, open Settings › Languages & Frameworks › Android SDK › SDK Tools, tick Show Package Details and untick old versions; or run sdkmanager --uninstall "build-tools;<version>" in Terminal (permanent).