Sill: Your Whole Mac on Your iPhone, in a 3.3 MB Open-Source App

0:00Sill streams any window from your Mac — or the whole desktop — live to your iPhone or iPad, where you drive it with touch, a keyboard, a trackpad, or an Apple Pencil. The headline: no account, no cloud, no server in between. Your Mac talks straight to your device. It's free, open source (Apache-2.0), and about three weeks old at the time of the video.

The 3.3 MB engineering

0:31The number that made the channel cover it: the entire Mac download is 3.3 megabytes — smaller than a single iPhone photo. That's what you get from a native Swift app with zero third-party dependencies: no Electron, no bundled browser engine, just Apple's frameworks. It's enforced — the project's contribution rules forbid outside dependencies, forbid anything needing a server, and put latency ahead of picture quality, in writing. It's built by one person, Noah (a senior software engineer in New York); at video time the repo was 22 days old with 585 commits, all his.

How it feels

1:41Pair each device once — scan a code or type 12 digits — and from then on every connection is pinned to those keys. Taps become clicks, scrolls carry momentum, three-finger swipes and pinches work like a Mac trackpad, so Mission Control and Spaces work from a slab of glass. The Apple Pencil becomes the pointer, you can launch any installed app from a searchable list, and the app's real menus reach the device. 2:10On a foldable iPhone Duo it follows the hinge (flat = full screen, half-open = trackpad below the fold, closed = the covered display), and if someone moves the mouse at the Mac itself, the pointer moves live on your device. 2:27The screenshot that sold the channel: laptop mode — hold an iPad upright and it stacks the Mac window on top with a row of keys and a trackpad below. Your iPad becomes a tiny MacBook whose brain is in the other room.

The plumbing

2:53Pure Apple plumbing, used properly: the Mac captures the window with ScreenCaptureKit and encodes it as HEVC on the hardware video encoder, so the stream costs almost nothing. It travels over TLS 1.3, pinned to the keys you paired — never through anyone's relay. Discovery is Bonjour on your network; plug in USB and it goes wired with no shared network at all; there's a peer-to-peer wireless mode like AirDrop; and away from home your own VPN (Tailscale is the README's example) carries it. When the link falls behind, Sill drops frames instead of queuing them, so the picture is always current. And when no device is connected, Sill captures nothing at all.

Why it can't ship on the App Store

5:29The reason, and it's the kind of detail that makes you respect the project more, not less: Sill's optional virtual display feature (the one that keeps a streamed window updating while other windows cover it) uses a private macOS API. Apple doesn't allow that in the Mac App Store, so the Mac app ships notarized from the website (getsill.app) instead. The developer's stated attitude is, plainly, "so." 5:47Same transparency on security: versions before 0.3.1 sent local traffic unencrypted, and the README documents it and tells you to update. One developer, 22 days of public life, 51 open issues — the bus factor is real, but this kind of upfront disclosure is exactly what trust looks like in open source.

The honest part

5:14The limits, stated plainly: Apple Silicon Mac on macOS 14+, iOS 17+ (Intel Macs are out); one window or one desktop at a time; and no sound yet. A quick clarification the video offers up front: Apple's Sidecar goes the other way (Mac → iPad as a second display); Sill is the reverse — your Mac in your pocket. Getting it is simple: a free notarized download from getsill.app for the Mac, a free App Store app for iPhone/iPad, or — since it's Apache-2.0 — build it yourself with one script (Swift Package Manager, your own signing identity, plus a synthetic test-pattern mode for development).

Claims checked

Sources & further reading