diff --git a/script/confirm-matches-djpeg.sh b/script/confirm-matches-djpeg.sh
new file mode 100755
index 0000000..20a2975
--- /dev/null
+++ b/script/confirm-matches-djpeg.sh
@@ -0,0 +1,73 @@
+#!/bin/bash -eu
+# Copyright 2023 The Wuffs Authors.
+#
+# 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
+#
+#    https://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.
+
+# ----------------
+
+# This script checks that Wuffs's JPEG decoder and djpeg (from libjpeg or
+# libjpeg-turbo) produce the same output (using djpeg's default configuration,
+# with no further command line arguments).
+
+if [ ! -e wuffs-root-directory.txt ]; then
+  echo "$0 should be run from the Wuffs root directory."
+  exit 1
+elif [ ! -e gen/bin/example-convert-to-nia ]; then
+  echo "Run \"./build-example.sh example/convert-to-nia\" first."
+  exit 1
+elif [ ! -e gen/bin/example-crc32 ]; then
+  echo "Run \"./build-example.sh example/crc32\" first."
+  exit 1
+elif [ -z $(which djpeg) ]; then
+  echo "Could not find \"djpeg\"."
+  exit 1
+fi
+
+sources=$@
+if [ $# -eq 0 ]; then
+  sources=test/data/*.jpeg
+fi
+
+# ----
+
+result=0
+
+handle() {
+  local have=$(gen/bin/example-convert-to-nia <$1 2>/dev/null | gen/bin/example-crc32)
+  local want=$(djpeg $1 2>/dev/null | gen/bin/example-convert-to-nia 2>/dev/null | gen/bin/example-crc32)
+  if [ "$want" != "00000000" ]; then
+    if [ "$want" == "$have" ]; then
+      echo "Match   $1"
+    else
+      echo "Differ  $1"
+      result=1
+    fi
+  fi
+}
+
+# ----
+
+for f in $sources; do
+  if [ -f $f ]; then
+    handle $f
+  elif [ -d $f ]; then
+    for g in `find $f -type f | LANG=C sort`; do
+      handle $g
+    done
+  else
+    echo "Could not open $f"
+    exit 1
+  fi
+done
+
+exit $result