1. Siri AI, Completely Rebuilt

Siri now has its own dedicated app (built with Google's Gemini model) alongside deep system-wide integration. It works much like a chatbot — keeping chat history, supporting search, and letting you pin important conversations.

2. Siri Lives Inside Spotlight

Press ⌘-Space and you'll see a new “Search or Ask” bar. The same window now handles both plain file/app search and full AI conversations — no more choosing between two tools.

3. Apple Silicon Only (M chip)

macOS 27 drops support for Intel-based Macs and Rosetta 2. If you're still on an Intel Mac, this is the last stop — a new Intel-App Checker in System Settings helps you find software that needs replacing first.

4. Refreshed Liquid Glass Design

The Red/Yellow/Green buttons get a classic Aqua-style glass redesign, window borders are consistent across all apps again, and the menu bar and widgets are refined and customizable.

5. Natural-Language Calendar Events

You can add or edit calendar events just by describing them in plain English. If you want to turn a lunch meeting into a coffee chat? Just edit the description — Calendar updates the details for you.

6. System-Wide Live Captions

Automatic, synced subtitles now work for any video you're watching, anywhere on the Mac — and you have the ability to translate existing captions into other languages.

7. Smarter VoiceOver

Accessibility gets a boost with richer, more accurate image descriptions and a better understanding of what's on your screen.

8. Automatic Password Clean-Up

When Siri AI flags a compromised or weak password in the Password App, it can now replace it with a strong one for you — no more manually hunting down and updating logins. (This feature will roll out in a point update, not certain of it’s arrival date)

9. Better Mail Search

Finally! A better reworked search in Mail gives a better-organized view of results — good news if you've ever relied on search instead of tidying your inbox.

10. Sharper Displays — and Cleanup Ahead

Ultrawide monitor owners can now get higher resolutions, such as 5K at 120Hz. Also note: Apple is phasing out built-in DVD playback, so this is likely the last macOS version to include it natively.