By default, the chat is persistent.This means that the room content will be kept for a while.User joining will see messages posted before their arrival.
You can change the persistence behaviour.[Open the chat dropdown menu](/peertube-plugin-livechat/documentation/user/viewers), and click on "Configure".
If you want to delete the chat content, [open the chat dropdown menu](/peertube-plugin-livechat/documentation/user/viewers), then click on "Destroy".A popup will open, asking a confirmation.
The chat will be automatically recreated each time someone tries to join it as long as the video exists, and has the "{{% livechat_label use_chat %}}" feature activated.