diff --git a/src/Kaleidoscope.h b/src/Kaleidoscope.h
index 57dbbe81..bf457698 100644
--- a/src/Kaleidoscope.h
+++ b/src/Kaleidoscope.h
@@ -80,6 +80,7 @@ void setup();
 #endif
 
 #include "kaleidoscope/KeyAddr.h"
+#include "kaleidoscope/KeyEvent.h"
 #include "kaleidoscope/key_events.h"
 #include "kaleidoscope/layers.h"
 #include "kaleidoscope_internal/sketch_exploration/sketch_exploration.h"
diff --git a/src/kaleidoscope/KeyEvent.cpp b/src/kaleidoscope/KeyEvent.cpp
new file mode 100644
index 00000000..c9d01704
--- /dev/null
+++ b/src/kaleidoscope/KeyEvent.cpp
@@ -0,0 +1,23 @@
+/* Kaleidoscope - Firmware for computer input devices
+ * Copyright (C) 2020  Keyboard.io, Inc.
+ *
+ * This program is free software: you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License as published by the Free Software
+ * Foundation, version 3.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "kaleidoscope/KeyEvent.h"
+
+namespace kaleidoscope {
+
+KeyEventId KeyEvent::last_id_ = 0;
+
+}  // namespace kaleidoscope
diff --git a/src/kaleidoscope/KeyEvent.h b/src/kaleidoscope/KeyEvent.h
new file mode 100644
index 00000000..0cc97ab8
--- /dev/null
+++ b/src/kaleidoscope/KeyEvent.h
@@ -0,0 +1,68 @@
+/* Kaleidoscope - Firmware for computer input devices
+ * Copyright (C) 2021  Keyboard.io, Inc.
+ *
+ * This program is free software: you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License as published by the Free Software
+ * Foundation, version 3.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <stdint.h>                 // for uint8_t, int8_t
+
+#include "kaleidoscope/key_defs.h"  // for Key, Key_NoKey
+#include "kaleidoscope/KeyAddr.h"   // for KeyAddr
+
+namespace kaleidoscope {
+
+// It's important that this is a signed integer, not unsigned. It should be
+// `int8_t`, but I changed it to 32 for debugging purposes.
+typedef int8_t KeyEventId;
+
+struct KeyEvent {
+
+ public:
+  // Constructor for plugin use when regenerating an event with specific ID:
+  KeyEvent(KeyAddr addr, uint8_t state,
+           Key key = Key_NoKey, KeyEventId id = last_id_)
+    : addr(addr), state(state), key(key), id_(id) {}
+
+  KeyEvent() : id_(last_id_) {}
+
+  // For use by keyscanner creating a new event from a physical keyswitch toggle
+  // on or off.
+  static KeyEvent next(KeyAddr addr, uint8_t state) {
+    return KeyEvent(addr, state, Key_NoKey, ++last_id_);
+  }
+
+  KeyEventId id() const {
+    return id_;
+  }
+  void swapId(KeyEvent &other) {
+    KeyEventId tmp_id = id_;
+    id_ = other.id_;
+    other.id_ = tmp_id;
+  }
+
+  KeyAddr addr = KeyAddr::none();
+  uint8_t state = 0;
+  Key key = Key_NoKey;
+
+ private:
+  // serial number of the event:
+  static KeyEventId last_id_;
+  KeyEventId id_;
+};
+
+}  // namespace kaleidoscope
+
+typedef kaleidoscope::KeyEventId KeyEventId;
+typedef kaleidoscope::KeyEvent KeyEvent;