Enable iMessage (Messages) Subject Field in macOS Big Sur through Sonoma

macos-messages-subject-field.md

Want the Subject field (for bold iMessages) in macOS’ Messages app?

1. Quit Messages
2. Open Terminal
3. Run defaults write com.apple.MobileSMS MMSShowSubject 1
4. Start Messages

This worked for me on a fresh install of macOS 14.1.1 (23B81) (new Mac mini).

This worked for me on a fresh install of macOS 14.1.1 (23B81) (new Mac mini).

No longer works in MacOS 15, know where this moved and how to enable it now?

No longer works in MacOS 15, know where this moved and how to enable it now?

You can edit the ~/Library/Preferences/com.apple.MobileSMS.plist directly. Quit Messages and add this right inside the first <dict>, after the opening tag:

<key>MMSShowSubject</key>
<true/>

defaults should normally edit this file too.

Thanks @2xsaiko, I tried this and it killed Messages. Had to revert the preference .plist to get it to work again.

Hmm, really? It worked for me. Though tbh I put it at the very bottom before the , but that shouldn't make a difference.

Very weird @2xsaiko, could you post / DM me your plist so I can copy that in and see if that works?

https://gist.github.com/2xsaiko/3604038825dc1118b81eda7c8f0ba1b3

@jbburf @2xsaiko can either of you identify the different between your two plists? It might be helpful for others and I can update the instructions if needed.

I mean that's really it, I just added it to the top level dict as I said. To the end that is, after I ran Messages again it rewrote the file and placed it somewhere in the middle, that's why it's no longer at the end in the paste.

It's probably safer to tell people to edit it with Xcode instead, there's no risk of messing up the file that way...