The user is preparing a message in a group — typing, recording, uploading, etc. This update is valid for 6 seconds. If no repeated update received after 6 seconds, it should be considered that the user stopped doing whatever he's been doing.
updateChatUserTyping#9a65ea1f chat_id:int user_id:int action:SendMessageAction = Update;
|action||SendMessageAction||Type of action
Parameter added in Layer 17.