diff --git a/esphome/components/web_server/web_server.cpp b/esphome/components/web_server/web_server.cpp
index 8ea1cf98c2..cab177c182 100644
--- a/esphome/components/web_server/web_server.cpp
+++ b/esphome/components/web_server/web_server.cpp
@@ -499,7 +499,8 @@ static void set_json_id(JsonObject &root, EntityBase *obj, const char *prefix, J
   // Build id into stack buffer - ArduinoJson copies the string
   // Format: {prefix}/{device?}/{name}
   // Buffer sizes use constants from entity_base.h validated in core/config.py
-  // Note: Device name (USE_DEVICES) uses ESPHOME_FRIENDLY_NAME_MAX_LEN, not ESPHOME_DEVICE_NAME_MAX_LEN
+  // Note: Device name uses ESPHOME_FRIENDLY_NAME_MAX_LEN (sub-device max 120), not ESPHOME_DEVICE_NAME_MAX_LEN
+  // (hostname)
 #ifdef USE_DEVICES
   static constexpr size_t ID_BUF_SIZE =
       ESPHOME_DOMAIN_MAX_LEN + 1 + ESPHOME_FRIENDLY_NAME_MAX_LEN + 1 + ESPHOME_FRIENDLY_NAME_MAX_LEN + 1;
diff --git a/esphome/core/entity_base.h b/esphome/core/entity_base.h
index 4ed6a8024a..dc961c3d84 100644
--- a/esphome/core/entity_base.h
+++ b/esphome/core/entity_base.h
@@ -16,7 +16,8 @@ namespace esphome {
 // Maximum device name length - keep in sync with validate_hostname() in esphome/core/config.py
 static constexpr size_t ESPHOME_DEVICE_NAME_MAX_LEN = 31;
 
-// Maximum friendly name length - keep in sync with friendly_name cv.Length(max=120) in esphome/core/config.py
+// Maximum friendly name length for entities and sub-devices - keep in sync with cv.Length(max=120) in
+// esphome/core/config.py
 static constexpr size_t ESPHOME_FRIENDLY_NAME_MAX_LEN = 120;
 
 // Maximum domain length (longest: "alarm_control_panel" = 19)