Update: The comments have an alternative method that works without installing anything and is retroactive. Unfortunately, that doesn't pull all Facebook chats, just the most recent ones
Finally, users can record and find Facebook chat history, but it requires a bit of a workaround including a Firefox plugin and a Facebook app. Not the most elegant solution, but for those who are just can’t seem to keep track of what they’re Facebook chatting about, it’ll have to do.
First, head over to the Facebook Chat History Manager homepage and install the plugin. It’ll prompt you over to the Facebook app after successful installation, where you’ll have to register the app and then create a local user account (all the chat history is stored on your own computer, not someone else’s servers).
The logs are also not particularly well formatted nor particularly intuitive to access. At any point in Firefox, you can just hit CTRL-ALT-F and the logs will come up, but there’s no easy way to click through to the logs inside Facebook itself, short of going to the application’s own URL. There’s also no way to search for chats, so you’re stuck either wading through them by date and name, and the output isn’t exactly well styled:
The good news is that these quibbles can probably be fixed with relatively minor updates, and the solutions gets bonus points for offline chat history access. In any case, it’s the best that can be done until Facebook unveils a chat history lookup of their own. If today’s announcement of improved Facebook inbox searching is any indication, that could be the near future.