diff --git a/tools/target_files_diff.py b/tools/target_files_diff.py
new file mode 100755
index 0000000..010ea84
--- /dev/null
+++ b/tools/target_files_diff.py
@@ -0,0 +1,224 @@
+#!/usr/bin/env python
+#
+# Copyright (C) 2009 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+#
+# Finds differences between two target files packages
+#
+
+from __future__ import print_function
+
+import argparse
+import contextlib
+import os
+import re
+import subprocess
+import tempfile
+
+def ignore(name):
+  """
+  Files to ignore when diffing
+
+  These are packages that we're already diffing elsewhere,
+  or files that we expect to be different for every build,
+  or known problems.
+  """
+
+  # We're looking at the files that make the images, so no need to search them
+  if name in ['IMAGES']:
+    return True
+  # These are packages of the recovery partition, which we're already diffing
+  if name in ['SYSTEM/etc/recovery-resource.dat',
+              'SYSTEM/recovery-from-boot.p']:
+    return True
+
+  # These files are just the BUILD_NUMBER, and will always be different
+  if name in ['BOOT/RAMDISK/selinux_version',
+              'RECOVERY/RAMDISK/selinux_version']:
+    return True
+
+  # b/24201956 .art/.oat/.odex files are different with every build
+  if name.endswith('.art') or name.endswith('.oat') or name.endswith('.odex'):
+    return True
+  # b/25348136 libpac.so changes with every build
+  if name in ['SYSTEM/lib/libpac.so',
+              'SYSTEM/lib64/libpac.so']:
+    return True
+
+  return False
+
+
+def rewrite_build_property(original, new):
+  """
+  Rewrite property files to remove values known to change for every build
+  """
+
+  skipped = ['ro.bootimage.build.date=',
+             'ro.bootimage.build.date.utc=',
+             'ro.bootimage.build.fingerprint=',
+             'ro.build.id=',
+             'ro.build.display.id=',
+             'ro.build.version.incremental=',
+             'ro.build.date=',
+             'ro.build.date.utc=',
+             'ro.build.host=',
+             'ro.build.description=',
+             'ro.build.fingerprint=',
+             'ro.expect.recovery_id=',
+             'ro.vendor.build.date=',
+             'ro.vendor.build.date.utc=',
+             'ro.vendor.build.fingerprint=']
+
+  for line in original:
+    skip = False
+    for s in skipped:
+      if line.startswith(s):
+        skip = True
+        break
+    if not skip:
+      new.write(line)
+
+
+def trim_install_recovery(original, new):
+  """
+  Rewrite the install-recovery script to remove the hash of the recovery partition.
+  """
+  for line in original:
+    new.write(re.sub(r'[0-9a-f]{40}', '0'*40, line))
+
+def sort_file(original, new):
+  """
+  Sort the file. Some OTA metadata files are not in a deterministic order currently.
+  """
+  lines = original.readlines()
+  lines.sort()
+  for line in lines:
+    new.write(line)
+
+# Map files to the functions that will modify them for diffing
+REWRITE_RULES = {
+    'BOOT/RAMDISK/default.prop': rewrite_build_property,
+    'RECOVERY/RAMDISK/default.prop': rewrite_build_property,
+    'SYSTEM/build.prop': rewrite_build_property,
+    'VENDOR/build.prop': rewrite_build_property,
+
+    'SYSTEM/bin/install-recovery.sh': trim_install_recovery,
+
+    'META/boot_filesystem_config.txt': sort_file,
+    'META/filesystem_config.txt': sort_file,
+    'META/recovery_filesystem_config.txt': sort_file,
+    'META/vendor_filesystem_config.txt': sort_file,
+}
+
+@contextlib.contextmanager
+def preprocess(name, filename):
+  """
+  Optionally rewrite files before diffing them, to remove known-variable information.
+  """
+  if name in REWRITE_RULES:
+    with tempfile.NamedTemporaryFile() as newfp:
+      with open(filename, 'r') as oldfp:
+        REWRITE_RULES[name](oldfp, newfp)
+      newfp.flush()
+      yield newfp.name
+  else:
+    yield filename
+
+def diff(name, file1, file2):
+  """
+  Diff a file pair with diff, running preprocess() on the arguments first.
+  """
+  with preprocess(name, file1) as f1:
+    with preprocess(name, file2) as f2:
+      proc = subprocess.Popen(['diff', f1, f2], stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
+      (stdout, ignore) = proc.communicate()
+      if proc.returncode == 0:
+        return
+      stdout = stdout.strip()
+      if stdout == 'Binary files %s and %s differ' % (f1, f2):
+        print("%s: Binary files differ" % name)
+      else:
+        for line in stdout.strip().split('\n'):
+          print("%s: %s" % (name, line))
+
+def recursiveDiff(prefix, dir1, dir2):
+  """
+  Recursively diff two directories, checking metadata then calling diff()
+  """
+  list1 = sorted(os.listdir(dir1))
+  list2 = sorted(os.listdir(dir2))
+
+  for entry in list1:
+    name = os.path.join(prefix, entry)
+    name1 = os.path.join(dir1, entry)
+    name2 = os.path.join(dir2, entry)
+
+    if ignore(name):
+      continue
+
+    if entry in list2:
+      if os.path.islink(name1):
+        if os.path.islink(name2):
+          link1 = os.readlink(name1)
+          link2 = os.readlink(name2)
+          if link1 != link2:
+            print("%s: Symlinks differ: %s vs %s" % (name, link1, link2))
+        else:
+          print("%s: File types differ, skipping compare" % name)
+        continue
+
+      stat1 = os.stat(name1)
+      stat2 = os.stat(name2)
+      type1 = stat1.st_mode & ~0777
+      type2 = stat2.st_mode & ~0777
+
+      if type1 != type2:
+        print("%s: File types differ, skipping compare" % name)
+        continue
+
+      if stat1.st_mode != stat2.st_mode:
+        print("%s: Modes differ: %o vs %o" % (name, stat1.st_mode, stat2.st_mode))
+
+      if os.path.isdir(name1):
+        recursiveDiff(name, name1, name2)
+      elif os.path.isfile(name1):
+        diff(name, name1, name2)
+      else:
+        print("%s: Unknown file type, skipping compare" % name)
+    else:
+      print("%s: Only in base package" % name)
+
+  for entry in list2:
+    name = os.path.join(prefix, entry)
+    name1 = os.path.join(dir1, entry)
+    name2 = os.path.join(dir2, entry)
+
+    if ignore(name):
+      continue
+
+    if entry not in list1:
+      print("%s: Only in new package" % name)
+
+def main():
+  parser = argparse.ArgumentParser()
+  parser.add_argument('dir1', help='The base target files package (extracted)')
+  parser.add_argument('dir2', help='The new target files package (extracted)')
+  args = parser.parse_args()
+
+  recursiveDiff('', args.dir1, args.dir2)
+
+if __name__ == '__main__':
+  main()