diff --git a/swh/scanner/cli.py b/swh/scanner/cli.py
--- a/swh/scanner/cli.py
+++ b/swh/scanner/cli.py
@@ -107,7 +107,7 @@
 
 
 @scanner.command(name="scan")
-@click.argument("root_path", required=True, type=click.Path(exists=True))
+@click.argument("root_path", default=".", type=click.Path(exists=True))
 @click.option(
     "-u",
     "--api-url",
@@ -129,9 +129,11 @@
     "-f",
     "--output-format",
     "out_fmt",
-    default="text",
+    default="summary",
     show_default=True,
-    type=click.Choice(["text", "json", "ndjson", "sunburst"], case_sensitive=False),
+    type=click.Choice(
+        ["summary", "text", "json", "ndjson", "sunburst"], case_sensitive=False
+    ),
     help="The output format",
 )
 @click.option(
@@ -158,6 +160,19 @@
     """Scan a source code project to discover files and directories already
     present in the archive.
 
+    The command can provide different output using the --output-format option:\n
+    \b
+      summary: display a general summary of what the scanner found
+
+      text: display the scan result as a text based tree-like view of all the
+            file, using color to indicate the file status.
+
+      json: write all collected data on standard output as JSON
+
+      json: write all collected data on standard output as Newline Delimited JSON
+
+      sunburst: produce a dynamic chart as .html file. (in $PWD/chart.html)
+
     The source code project can be checked using different policies that can be set
     using the -p/--policy option:\n
     \b
diff --git a/swh/scanner/output.py b/swh/scanner/output.py
--- a/swh/scanner/output.py
+++ b/swh/scanner/output.py
@@ -40,7 +40,9 @@
         self.source_tree = source_tree
 
     def show(self, mode=DEFAULT_OUTPUT):
-        if mode == "text":
+        if mode == "summary":
+            self.summary()
+        elif mode == "text":
             isatty = sys.stdout.isatty()
             self.print_text(isatty)
         elif mode == "sunburst":
@@ -90,6 +92,55 @@
 
         print(f"{begin}{rel_path}{end}")
 
+    def summary(self):
+        directories_with_known_files = set()
+
+        total_files = 0
+        total_directories = 0
+        known_files = 0
+        full_known_directories = 0
+        partially_known_directories = 0
+
+        contents = []
+        directories = []
+
+        for node in self.source_tree.iter_tree():
+            if node.object_type == "content":
+                contents.append(node)
+            elif node.object_type == "directory":
+                directories.append(node)
+            else:
+                assert False, "unreachable"
+
+        total_files = len(contents)
+        for c in contents:
+            if self.nodes_data[c.swhid()]["known"]:
+                known_files += 1
+                path = c.data[self.get_path_name(c)]
+                dir_name = os.path.dirname(path)
+                directories_with_known_files.add(dir_name)
+
+        total_directories = len(directories)
+        for d in directories:
+            if self.nodes_data[d.swhid()]["known"]:
+                full_known_directories += 1
+            else:
+                path = d.data[self.get_path_name(d)]
+                if path in directories_with_known_files:
+                    partially_known_directories += 1
+
+        kp = known_files * 100 // total_files
+        fkp = full_known_directories * 100 // total_directories
+        pkp = partially_known_directories * 100 // total_directories
+        print("Files:            ", f"{total_files:10d}")
+        print("            known:", f"{known_files:10d}", f"  ({kp:3d}%)")
+        print("directories:      ", f"{total_directories:10d}")
+        print("      fully-known:", f"{full_known_directories:10d}", f"  ({fkp:3d}%)")
+        print(
+            "  partially-known:", f"{partially_known_directories:10d}", f"  ({pkp:3d}%)"
+        )
+        print("(see other --output-format for more details)")
+
     def data_as_json(self):
         json = {}
         for node in self.source_tree.iter_tree():