diff --git a/stsp/swh-diff.py b/stsp/swh-diff.py
new file mode 100755
--- /dev/null
+++ b/stsp/swh-diff.py
@@ -0,0 +1,52 @@
+#!/usr/bin/python3
+# Copyright (C) 2021  The Software Heritage developers
+# License: GNU Affero General Public License version 3, or any later version
+# See top-level LICENSE file for more information
+
+# Display a unified diff showing the changes made in a revision.
+
+import sys
+import difflib
+
+from swh.storage import get_storage
+from swh.model.hashutil import hash_to_bytes
+from swh.storage.algos.diff import diff_revision
+
+if __name__ == "__main__":
+    if len(sys.argv) == 2:
+        rev_id = hash_to_bytes(sys.argv[1])
+        storage_url = "http://127.0.0.1:5002"
+    elif len(sys.argv) == 3:
+        rev_id = hash_to_bytes(sys.argv[1])
+        storage_url = sys.argv[2]
+    else:
+        print("usage: revision [storage-url]")
+        sys.exit(1)
+
+    storage = get_storage("remote", url=storage_url)
+
+    diffs = diff_revision(storage, rev_id)
+    for d in diffs:
+        if d['type'] == 'modify':
+            from_path = d['from_path']
+            to_path = d['to_path']
+            from_data = storage.content_get_data(d['from']['sha1'])
+            to_data = storage.content_get_data(d['to']['sha1'])
+        elif d['type'] == 'insert':
+            from_path = b'/dev/null'
+            to_path = d['to_path']
+            from_data = b''
+            to_data = storage.content_get_data(d['to']['sha1'])
+        elif d['type'] == 'delete':
+            from_path = d['to_path']
+            to_path = b'/dev/null'
+            from_data = storage.content_get_data(d['from']['sha1'])
+            to_data = b''
+        else:
+            continue
+
+        unidiff = difflib.diff_bytes(difflib.unified_diff,
+            from_data.splitlines(keepends=True),
+            to_data.splitlines(keepends=True),
+            from_path, to_path)
+        sys.stdout.buffer.writelines(unidiff);