High Performance mode allows sharing another Mac’s display as if your own

Apple’s built-in screen sharing support for Mac-to-Mac connections has always been a help for those of us with remote setups: headless Macs acting as servers, an office and home Mac, or the laziness of having Macs in different parts of your house you want to access without standing up.1

Under the hood, Apple relies on VNC (Virtual Network Computing), a fairly ancient standard at this point in time, and you probably get the sense of its creaking joints if you use the Screen Sharing app regularly.2 But it’s possible you didn’t know that, starting in Sonoma, Apple added a “super excellent” mode to Screen Sharing as an option when you connect two Macs with M-series chips. Called High Performance, it can deliver on its name.

Let’s shift into overdrive

When you initiate a connection, Screen Sharing asks you to pick between Standard and High Performance modes.

When you connect to another Mac using Screen Sharing, you’re given a choice of which mode to use. Let’s walk through the connection steps:

Either launch the Screen Sharing app and double-click the Mac’s name in a list, or, in the Finder, Control-click/right-click the Mac’s name and choose Screen Sharing. (There are still more ways to start, too.)

From the Select Screen Sharing Type options, you can select Standard, which is VNC-based, or High Performance, which adds Apple’s secret sauce on top.

Click Continue.

Enter your credentials.

The screen appears, and you may need to enter your macOS account password on the remote Mac to unlock it.

In that pathway, if you choose High Performance, you’re presented with different options. You can also click the info (i) button to the right of an existing connection in the Connections window in Screen Sharing, and choose High Performance from the Screen Sharing Type pop-up menu to save that option for the next connection.

A saved connection’s settings let you change the sharing type, display configuration, and port after the fact.

With a Standard connection, you get a pixel-for-pixel remote view of the other Mac’s display or displays. It’s just like you’re sitting in front of it. In fact, if you use the same account as the currently logged-in user, the remote Mac shows what you’re doing to anyone who looks at it. (You can log in as another user, and a session starts in the background that doesn’t appear on the remote display screen.)

High Performance takes a different approach. You can opt to create one or two virtual displays on the remote Mac, each with independent resolution, high-dynamic-range (HDR) support, and other features. It’s like being a remote user of the computer rather than sharing. (This mode doesn’t change the remote display resolution or other settings.)

With a High Performance connection between Apple silicon Macs, you gain these advantages:

You can choose one or two virtual displays, regardless of the number of displays connected to the shared computer.

The Dynamic Resolution option lets you resize a virtual display to the native resolution of your local screen, up to 4K (3840×2160 pixels) or, with HiDPI, up to 1920×1080. You can click the Dynamic button on the Screen Sharing toolbar or choose View: Dynamic Resolution during a live session.

Stereo audio passes over the connection, as does improved video. The connection supports HDR (for richer low-light and shadow tones), 4:4:4 chroma subsampling (uncompressed color data for improved fidelity), and high frame rates of 30 or 60 frames per second (for more stable video streaming, such as when watching a video or using video-editing software).

The downside of High Performance is that it imposes severe requirements for it to work well. You need 75 Mbps per 4K display and low network latency, which requires fast Wi-Fi with a gigabit-or-faster mesh or wired backbone if there are multiple network routers or base stations. However, that requirement also means that when you’re using High Performance, it feels very much like sitting in front of the other display rather than viewing it remotely.

The Screen Sharing toolbar with High Performance mode enabled offers controls unavailable in a Standard session; some options remain dimmed depending on the remote Mac’s capabilities.

If you want the depth of HDR Video, you have to enable it on the remote Mac via System Settings: Displays. The option for HDR Video appears in a Preset pop-up menu, but, of course, only if the display supports the right HDR signal. HDR can be enabled or disabled from the View menu and Screen Sharing toolbar, if it’s available.

Because the remote display is blacked out when using High Performance (even when connecting as the currently logged-in user), this can be seen as a privacy advantage if you have concerns about anyone else viewing the remote Mac’s screen. However, High Performance mode’s utility really lies in treating Screen Sharing like a high-speed display tunnel instead of a jerky remote view.

For further reading

If you’re looking for more detailed information about High Performance mode or any aspect of Mac-based file and screen sharing, you might consult my book, Take Control of Apple Screen and File Sharing.

[Got a question for the column? You can email glenn@sixcolors.com or use /glenn in our subscriber-only Discord community.]

I don’t have a couch Mac and a kitchen Mac and a bedroom Mac and a… you get it. But I do have a downstairs office Mac and a laptop. ↩

Screen Sharing is found in /System/Applications/Utilities, just an oddity of how Apple locates certain apps on the immutable System volume. ↩