new file mode 100644
--- /dev/null
+++ b/.clang-format
@@ -0,0 +1,1 @@
+BasedOnStyle: Mozilla

--- a/.clang-format-ignore
+++ b/.clang-format-ignore
@@ -1,2 +1,3 @@
 \mfbt/
 \js/
+\media/

--- a/tools/mach_commands.py
+++ b/tools/mach_commands.py
@@ -351,17 +351,17 @@ class FormatProvider(MachCommandBase):
 
         except urllib2.HTTPError as e:
             print("HTTP error {0}: {1}".format(e.code, e.reason))
             return 1
 
         from subprocess import Popen, PIPE
         p1 = Popen(["hg", "diff", "-U0", "-r", "tip^", "--include", "glob:**.c", "--include", "glob:**.cpp",
                    "--include", "glob:**.h", "--exclude", "listfile:.clang-format-ignore"], stdout=PIPE)
-        args = [sys.executable, clang_format_diff, "-p1", "-style=Mozilla"]
+        args = [sys.executable, clang_format_diff, "-p1"]
         if not show:
            args.append("-i")
         p2 = Popen(args, stdin=p1.stdout)
         return p2.communicate()[0]
 
     def locate_or_fetch(self, root):
         target = os.path.join(self._mach_context.state_dir, os.path.basename(root))
         if not os.path.exists(target):