diff --git a/bp2build/constants.go b/bp2build/constants.go
new file mode 100644
index 0000000..23bca83
--- /dev/null
+++ b/bp2build/constants.go
@@ -0,0 +1,25 @@
+// Copyright 2020 Google Inc. All rights reserved.
+//
+// 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.
+
+package bp2build
+
+var (
+	// When both a BUILD and BUILD.bazel file are exist in the same package, the BUILD.bazel file will
+	// be preferred for use within a Bazel build.
+
+	// The file name used for automatically generated files. Files with this name are ignored by git.
+	GeneratedBuildFileName = "BUILD"
+	// The file name used for hand-crafted build targets.
+	HandcraftedBuildFileName = "BUILD.bazel"
+)