If you're a user of Messages on Mac, then you might have noticed that the app tends to keep track of all your conversations automatically. That's great for most of us, but if you need to delete those conversations, it's a little difficult. Tech blog Addictive Tips shows how to do it.
You can disable chat history right in the Messages preferences panel to get rid of any conversations you might have in the future, but older conversations will stick around. This includes conversations you have in GChat, even if you disabled chat history on the Google end, and any conversations in iMessage.
The tricky part is that the conversations are stored in a hidden folder. To get to them, head to Finder, hit Go > Go to Folder and enter in ~/Library/Messages/Archive. Delete all the old messages and they'll be gone forever. Head over to Addictive Tips for tips on deleting single conversations and a few other tips for keeping your conversations stealthy.
How To Disable And Delete Chat History In OS X Messages [Addictive Tips]