When I delete messages on my iPhone they don't automatically delete on my Mac. What can I do to fix this?

Hello NellyEmmaLola123,

If you have iCloud for Messages set up, your messages should be the same on all devices:

Access the same messages on all your devices

When you set up iCloud for Messages, your messages are stored in the cloud instead of locally on your device. You can see them on any device that’s set up for iCloud and Messages, including your iPhone, iPad, iPod touch, and Mac.

Because your messages are in the cloud, if you send, receive, or delete a message on one device, those updates appear everywhere. You see the most up-to-date version of your messages, no matter where you access them.

Keep your messages up to date with iCloud - Apple Support

You can find steps for setting up iCloud for Messages here: Set up iCloud for Messages on all your devices - Apple Support

We hope that helps.

Take care.