Can see both deleted and edited messages. Cons: Violates Discord's Terms of Service and can lead to account bans. Data Scraping Tools
For individual DMs, take screenshots of important conversations as they occur. recover-deleted-messages-on-discord
Third-party client mods like MessageLoggerV3 save local copies of all incoming chat. Can see both deleted and edited messages
Personal backup. Cons: Technically complex and potentially unsafe. Security Warning: Scams to Avoid 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.