Clean Up Xcode Build Data Left Behind by Git Worktrees

#!/bin/bash
# derived-data-report.sh
# Maps each Xcode DerivedData folder to the project or Git worktree that
# created it, shows its size and last use, and flags folders whose project
# path no longer exists (for example after `git worktree remove`).
#
# Read-only by default. With --delete-missing it removes only folders whose
# recorded project path is gone, after showing each one and asking first.
#
# Usage:  bash derived-data-report.sh
#         bash derived-data-report.sh --root /path/to/custom/DerivedData
#         bash derived-data-report.sh --prefix ~/code/myapp
#         bash derived-data-report.sh --delete-missing [--yes]
# Guide:  https://appscreens.com/blog/xcode-derived-data-git-worktrees
# Tested: macOS 26.7, Xcode 27.2 (bash 3.2).
# SPDX-License-Identifier: MIT
# Copyright (c) 2026 AppScreens. Free to use, copy and change; please keep
# this header, including the guide link.

set -u
ROOTS=""; PREFIX=""; DELETE=0; YES=0
while [ $# -gt 0 ]; do
  case "$1" in
    --root) ROOTS="$ROOTS
$2"; shift ;;
    --prefix) PREFIX=${2%/}; shift ;;
    --delete-missing) DELETE=1 ;;
    --yes) YES=1 ;;
    -h|--help) sed -n '2,16p' "$0"; exit 0 ;;
    *) echo "Unknown option: $1" >&2; exit 1 ;;
  esac
  shift
done

# DerivedData roots: the default, a custom location set in Xcode settings,
# roots recorded in Xcode's own location log, and any --root you pass.
DEFAULT="$HOME/Library/Developer/Xcode/DerivedData"
CUSTOM=$(defaults read com.apple.dt.Xcode IDECustomDerivedDataLocation 2>/dev/null || true)
KNOWN=$(grep -o '"/[^"]*"' "$HOME/Library/Developer/Xcode/.knownDerivedDataLocations.log" 2>/dev/null | tr -d '"' | grep -v '\.app$' || true)
ROOTS=$(printf "%s\n%s\n%s\n%s\n" "$DEFAULT" "$CUSTOM" "$KNOWN" "$ROOTS" | sed 's:/*$::' | grep -v '^$' | sort -u)

human() { awk -v k="$1" 'BEGIN { if (k >= 1048576) printf "%.1f GB", k / 1048576; else if (k >= 1024) printf "%.0f MB", k / 1024; else printf "%d KB", k }'; }

# Xcode records some paths without the /private prefix (/tmp, /var).
exists() { [ -e "$1" ] || [ -e "/private$1" ]; }

describe() {  # what the recorded project path is today
  local wp=$1 dir top gd cd
  if ! exists "$wp"; then echo "MISSING"; return; fi
  case "$wp" in
    *.xcodeproj|*.xcworkspace|*.playground) dir=$(dirname "$wp") ;;
    *) dir=$wp ;;  # Swift packages record the package folder itself
  esac
  [ -d "$dir" ] || dir="/private$dir"
  top=$(git -C "$dir" rev-parse --show-toplevel 2>/dev/null) || { echo "exists"; return; }
  gd=$(cd "$dir" && cd "$(git rev-parse --git-dir)" && pwd -P)
  cd=$(cd "$dir" && cd "$(git rev-parse --git-common-dir)" && pwd -P)
  if [ "$gd" != "$cd" ]; then
    echo "worktree:$(git -C "$dir" branch --show-current 2>/dev/null)"
  else
    echo "main:$(git -C "$dir" branch --show-current 2>/dev/null)"
  fi
}

TMP=$(mktemp -t derived-data-report)
trap 'rm -f "$TMP" "$TMP.2"' EXIT
echo "$ROOTS" | while read -r root; do
  [ -d "$root" ] || continue
  for d in "$root"/*/; do
    d=${d%/}
    [ -d "$d" ] || continue
    wp=""; [ -f "$d/info.plist" ] && wp=$(/usr/libexec/PlistBuddy -c 'Print :WorkspacePath' "$d/info.plist" 2>/dev/null)
    if [ -z "$wp" ]; then
      if [[ $(basename "$d") =~ -[a-z]{28}$ ]]; then state="no info.plist"; else state="shared cache (keep)"; fi
      last="-"
    else
      state=$(describe "$wp")
      last=$(/usr/libexec/PlistBuddy -c 'Print :LastAccessedDate' "$d/info.plist" 2>/dev/null | awk '{print $2, $3, $6}')
    fi
    k=$(du -sk "$d" 2>/dev/null | cut -f1)
    printf "%s\t%s\t%s\t%s\t%s\n" "$k" "$state" "$last" "$d" "${wp:--}" >> "$TMP"
  done
done

# A folder without info.plist that shares its 28-letter hash with a recorded
# folder belongs to the same project (Xcode can create both for one worktree).
# Then keep only projects under --prefix, if one was given.
awk -F'\t' -v OFS='\t' -v prefix="$PREFIX" '
  function hash(path,   n) { n = path; sub(/.*\//, "", n); sub(/.*-/, "", n); return n }
  NR == FNR { if ($5 != "-") { st[hash($4)] = $2; wp[hash($4)] = $5 } next }
  {
    h = hash($4)
    if ($2 == "no info.plist" && length(h) == 28 && (h in st)) { $2 = st[h]; $3 = "companion"; $5 = wp[h] }
    if (prefix != "") {
      p2 = prefix; sub(/^\/private/, "", p2)
      if ($5 == "-" || (index($5, prefix) != 1 && index($5, p2) != 1 && index($5, "/private" p2) != 1)) next
    }
    print
  }' "$TMP" "$TMP" > "$TMP.2" && mv "$TMP.2" "$TMP"

if [ ! -s "$TMP" ]; then echo "No DerivedData folders found."; exit 0; fi

printf "%-9s  %-26s %-12s %s\n" "SIZE" "PROJECT PATH" "LAST USED" "DERIVED DATA FOLDER -> PROJECT"
sort -t$'\t' -k2,2 -k1,1rn "$TMP" | while IFS=$'\t' read -r k state last d wp; do
  printf "%-9s  %-26s %-12s %s\n" "$(human "$k")" "$state" "$last" "$(basename "$d")"
  [ "$wp" != "-" ] && printf "%-9s  %-26s %-12s   -> %s\n" "" "" "" "$wp"
done
miss=$(awk -F'\t' '$2 == "MISSING" { n++; k += $1 } END { printf "%d %d", n, k }' "$TMP")
printf "\n%s folder(s) point to a project path that no longer exists (%s).\n" "${miss% *}" "$(human "${miss#* }")"

[ $DELETE -eq 1 ] || { echo "Nothing was deleted. Re-run with --delete-missing to remove those folders."; exit 0; }
if pgrep -xq Xcode; then echo "Xcode is running. Quit Xcode first so it does not recreate or hold these folders." >&2; exit 1; fi
awk -F'\t' '$2 == "MISSING" { print $4 }' "$TMP" | while read -r d; do
  case "$(basename "$d")" in *-[a-z]*) ;; *) echo "Skipping unexpected name: $d"; continue ;; esac
  if [ $YES -eq 0 ]; then
    printf "Delete %s? [y/N] " "$d"; read -r answer < /dev/tty
    [ "$answer" = "y" ] || { echo "kept"; continue; }
  fi
  rm -rf "$d" && echo "deleted $d"
done

git worktree remove ../myapp-feature
bash derived-data-report.sh --prefix ~/code/myapp

bash derived-data-report.sh --prefix ~/code/myapp --delete-missing

for p in ~/Library/Developer/Xcode/DerivedData/*/info.plist; do
  wp=$(/usr/libexec/PlistBuddy -c 'Print :WorkspacePath' "$p" 2>/dev/null) || continue
  [ -e "$wp" ] || [ -e "/private$wp" ] || echo "$(dirname "$p")  ->  $wp"
done

AppScreens.com, "Clean Up Xcode Build Data Left Behind by Git Worktrees", 3 November 2026. https://appscreens.com/blog/xcode-derived-data-git-worktrees