The only user data collected and saved is your user ID and current username. This is used to store information linked to your account, such as bank balance, server XP, and work cooldown. Usernames may also be stored to improve searching for users to moderate servers. No identifying information is stored apart from these, and username history is not saved.

Server data collection matches that of user data. The server ID is collected to store information linked to that server, such as the bot prefix and configured channels for things such as welcome and goodbye messages. Like user data, the only identifying server data that gets stored is the ID itself.

HaileyBot does not log or save any message data. Server administrators can choose to enable a modlog feature, where messages will appear in the designated channel if edited or deleted. For this feature to work, message content needs to be stored in RAM, so HaileyBot keeps a cache of messages for 24 hours. The cache is never saved to disk, and in the event of a restart will be cleared automatically. An example of the modlog feature can be seen in the publicly viewable #mod-log channel of HaileyBot's support server.