So you are trying to find your old messages or need to find an old iMessage attachment? To access your past conversations, launch the Finder from the “Go” menu. Hold the “Option” key and press “Library” from the menu. Then Click the “Messages” and “Archive” Folder. You see two folders: Archive and Attachments along with a file database labeled “chat.db.”
iMessage files stored: The Good News
On Macs, your computer stores all your iMessages on your hard drive. Apple stores your Messages locally and not on its servers unless you backup to iCloud. Your messages and photos, videos, or any other attachments automatically sync and store in ~/Library/Messages/Archives and ~/Library/Messages/Attachments.
The Archive Folder holds all your past messages from saved or closed conversations. The Attachments Folder has any images or videos from those iMessage conversations. Additionally, Apple places your iMessages in the chat.db items in ~/Library/Messages. The chat.db keeps all your iMessage data from all of your current and active message histories. TextEdit or similar programs open these chat files, and some of the everyday languages are legible. BUT there is a lot of other info that’s not readable. Apple saves your conversations by each session, usually between each shutdown. Sleep and closing the Message app several times a day also creates additional sessions.
Along with ~/Library/Messages and Chat.db, some of your iMessages “history” is stored in Saved Chats located in ~/Library/Containers/com.apple.ichat/Data/Library/Messages/Archive. Remember, to access the ~/Library, use the Finder > Go Menu while holding down the ALT key which then displays the Library. Or just copy the path(s) above and use the Finder > Go menu > Go to Folder and paste these locations into the dialogue box.
iMessage files stored: The Bad News
Unfortunately, the Attachment Folder is a backup for your iMessages and Message app. And the interior folder names don’t make any logical sense. BUT, your images and videos are there. You just have to spend some time looking around to find the exact attachment, photo, or video you want.