If you need to ensure messages are preserved for evidence or archival:

Third-party client mods like MessageLoggerV3 save local copies of all incoming chat. recover-deleted-messages-on-discord

Bots like Dyno or MEE6 can be configured to log message events to a private moderator channel. If you need to ensure messages are preserved

Users can request a copy of their personal data via User Settings > Privacy & Safety . However, this typically only includes messages that currently exist; manually deleted messages are usually excluded from these archives. Methods for Viewing Deleted Messages recover-deleted-messages-on-discord

Be extremely cautious of "recovery services" or tools that ask for your Discord token, password, or to run code in your browser console.

Only use reputable bots from verified developers to log server activity. How to Prevent Future Loss