Engineering · Oct 25, 2026 · 2 min read
How Device MCP gets a sharper mirror than Device Hub
iOS 27 can stream a device's screen in several quality profiles. Device Hub asks for one capped at 6 Mbit/s. Device MCP asks for the one built for remote desktops.
By The Device MCP team
The first thing people notice in Device MCP is the picture. Moving content, from Liquid Glass to page swipes and scrolling lists, stays sharp where other mirrors smear. That isn't a decoder trick. We ask the device for a better stream.
One session, several profiles
On iOS 27, a Mac can open a screen-sharing session to a device over its developer connection. When the session starts, the Mac sends an offer that says what kind of stream it wants, and the device picks its encoder settings from that.
The offer Xcode's Device Hub sends selects iOS's screen-sharing profile. On iOS 27 that profile is limited to between 0.33 and 6 Mbit/s with 4:2:0 colour. While the screen moves, frames shrink to a few kilobytes and fine detail is the first thing to go.
The same session accepts other profiles. The one built for remote desktops streams between 20 and 60 Mbit/s in full-colour HEVC 4:4:4:
| Profile | Bitrate | Colour |
|---|---|---|
| Screen sharing (Device Hub) | 0.33–6 Mbit/s | 4:2:0 |
| Remote desktop (Device MCP's default) | 20–60 Mbit/s | 4:4:4 |
On an iPad Air, page swipes run at roughly 22–32 Mbit/s with frames of 50–100 KB, against 5–13 KB with the screen-sharing profile. Touch, buttons, the keyboard and rotation work exactly the same.
Colour you can trust
The device converts its Display P3 screen to sRGB before encoding, but it doesn't tag the stream with its colour space. Left alone, the decoder guesses, and mid-tones come out visibly lighter than on the device. Device MCP fills in the missing tags, so the mirror lands within about one level of the device's own lossless screenshot. That matters when you're checking a design.
When it falls back
Full-colour HEVC needs a hardware decoder. Apple silicon decodes it in a couple of milliseconds a frame. On a Mac without one, Device MCP asks for the standard profile instead of burning CPU cores on software decoding. If a device ever refuses the remote-desktop profile, Device MCP falls back the same way and tries again on the next connection. You can also choose Standard in Settings › General › Mirror Quality, which helps on a crowded Wi-Fi network.
The Inspector's Quality section shows exactly what you're getting: profile, resolution, frame rate and bitrate.