diff --git a/packager/hls/base/master_playlist.cc b/packager/hls/base/master_playlist.cc
index 3635f15d99..85783c5494 100644
--- a/packager/hls/base/master_playlist.cc
+++ b/packager/hls/base/master_playlist.cc
@@ -15,6 +15,7 @@
 #include "packager/base/strings/stringprintf.h"
 #include "packager/file/file.h"
 #include "packager/hls/base/media_playlist.h"
+#include "packager/hls/base/tag.h"
 #include "packager/version/version.h"
 
 namespace shaka {
@@ -63,47 +64,6 @@ std::list<Variant> AudioGroupsToVariants(
   return variants;
 }
 
-class Tag {
- public:
-  Tag(const std::string& name, std::string* buffer) : buffer_(buffer) {
-    base::StringAppendF(buffer_, "%s:", name.c_str());
-  }
-
-  void AddString(const std::string& key, const std::string& value) {
-    NextField();
-    base::StringAppendF(buffer_, "%s=%s", key.c_str(), value.c_str());
-  }
-
-  void AddQuotedString(const std::string& key, const std::string& value) {
-    NextField();
-    base::StringAppendF(buffer_, "%s=\"%s\"", key.c_str(), value.c_str());
-  }
-
-  void AddNumber(const std::string& key, uint64_t value) {
-    NextField();
-    base::StringAppendF(buffer_, "%s=%" PRIu64, key.c_str(), value);
-  }
-
-  void AddResolution(const std::string& key, uint32_t width, uint32_t height) {
-    NextField();
-    base::StringAppendF(buffer_, "%s=%" PRIu32 "x%" PRIu32, key.c_str(), width,
-                        height);
-  }
-
- private:
-  Tag(const Tag&) = delete;
-  Tag& operator=(const Tag&) = delete;
-
-  std::string* buffer_;
-  size_t fields = 0;
-
-  void NextField() {
-    if (fields++) {
-      buffer_->append(",");
-    }
-  }
-};
-
 void BuildAudioTag(const std::string& base_url,
                    const std::string& group_id,
                    const MediaPlaylist& audio_playlist,
diff --git a/packager/hls/base/tag.cc b/packager/hls/base/tag.cc
new file mode 100644
index 0000000000..995038096c
--- /dev/null
+++ b/packager/hls/base/tag.cc
@@ -0,0 +1,50 @@
+// Copyright 2018 Google Inc. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+
+#include "packager/hls/base/tag.h"
+
+#include <inttypes.h>
+
+#include "packager/base/strings/stringprintf.h"
+
+namespace shaka {
+namespace hls {
+
+Tag::Tag(const std::string& name, std::string* buffer) : buffer_(buffer) {
+  base::StringAppendF(buffer_, "%s:", name.c_str());
+}
+
+void Tag::AddString(const std::string& key, const std::string& value) {
+  NextField();
+  base::StringAppendF(buffer_, "%s=%s", key.c_str(), value.c_str());
+}
+
+void Tag::AddQuotedString(const std::string& key, const std::string& value) {
+  NextField();
+  base::StringAppendF(buffer_, "%s=\"%s\"", key.c_str(), value.c_str());
+}
+
+void Tag::AddNumber(const std::string& key, uint64_t value) {
+  NextField();
+  base::StringAppendF(buffer_, "%s=%" PRIu64, key.c_str(), value);
+}
+
+void Tag::AddResolution(const std::string& key,
+                        uint32_t width,
+                        uint32_t height) {
+  NextField();
+  base::StringAppendF(buffer_, "%s=%" PRIu32 "x%" PRIu32, key.c_str(), width,
+                      height);
+}
+
+void Tag::NextField() {
+  if (fields++) {
+    buffer_->append(",");
+  }
+}
+
+}  // namespace hls
+}  // namespace shaka
diff --git a/packager/hls/base/tag.h b/packager/hls/base/tag.h
new file mode 100644
index 0000000000..d3e7c4e17e
--- /dev/null
+++ b/packager/hls/base/tag.h
@@ -0,0 +1,46 @@
+// Copyright 2018 Google Inc. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+
+#ifndef PACKAGER_HLS_BASE_TAG_H_
+#define PACKAGER_HLS_BASE_TAG_H_
+
+#include <string>
+
+namespace shaka {
+namespace hls {
+
+/// Tag is a string formatting class used to build HLS tags that contain
+/// argument lists.
+class Tag {
+ public:
+  Tag(const std::string& name, std::string* buffer);
+
+  /// Add a non-quoted string value to the argument list.
+  void AddString(const std::string& key, const std::string& value);
+
+  /// Add a quoted string value to the argument list.
+  void AddQuotedString(const std::string& key, const std::string& value);
+
+  /// Add a non-quoted numeric value to the argument list.
+  void AddNumber(const std::string& key, uint64_t value);
+
+  /// Add a resolution value (AxB) to the argument list.
+  void AddResolution(const std::string& key, uint32_t width, uint32_t height);
+
+ private:
+  Tag(const Tag&) = delete;
+  Tag& operator=(const Tag&) = delete;
+
+  std::string* const buffer_;
+  size_t fields = 0;
+
+  void NextField();
+};
+
+}  // namespace hls
+}  // namespace shaka
+
+#endif  // PACKAGER_HLS_BASE_TAG_H_
diff --git a/packager/hls/hls.gyp b/packager/hls/hls.gyp
index 1569cb2bb0..f1c94dd521 100644
--- a/packager/hls/hls.gyp
+++ b/packager/hls/hls.gyp
@@ -20,6 +20,8 @@
         'base/media_playlist.h',
         'base/simple_hls_notifier.cc',
         'base/simple_hls_notifier.h',
+        'base/tag.cc',
+        'base/tag.h',
         'public/hls_params.h',
       ],
       'dependencies': [