Sill for Mac and iPhone, window sharing with local control

Sill's window-level control model

Sill addresses a specific gap between viewing a Mac remotely and controlling a particular application on a mobile device. The Mac application can show one window or the whole desktop on an iPhone or iPad. Once the image is visible, taps, clicks, scrolls, keys and Apple Pencil gestures travel back to the Mac. That model is different from making the phone the primary computer: the Mac still runs the application, while Sill provides a remote view and a return path for input.

The project is aimed at people who want to reach a Mac application from another Apple device, especially when a full desktop view is unnecessary. Sill's documentation highlights iPhone layouts, iPad window thumbnails, a laptop-style arrangement with keys and a trackpad, and iPhone Duo support that follows the hinge. It also supports connecting through a USB cable, local Wi-Fi, Direct Wireless Connection, or the user's own VPN such as Tailscale. Remote Access is disabled by default.

There is no Sill account in the documented workflow, and no server is placed between the Mac and the mobile app. That does not mean every connection is automatically safe on an arbitrary network. TLS 1.3 is used for the encrypted connection, and each paired device retains the other endpoint's key so later connections are pinned to those keys.

Capture, HEVC encoding and input return

The Mac side performs the capture and encoding work. Sill for Mac uses ScreenCaptureKit to capture the selected window or desktop and VideoToolbox to encode the result as HEVC. The README states that encoding normally uses the Mac's hardware video encoder, with software encoding used while the hardware encoder is busy. Nothing is captured while no device is connected, according to the project's description.

The encoded picture goes directly to Sill on the iPhone or iPad, where it is decoded and displayed. The mobile app sends input over the same connection. The Mac turns that input into mouse and keyboard events. This explains why the Mac requires Accessibility permission: clicks, scrolling, typing and commands for window manipulation depend on that access.

Sill applies a freshness policy when encoding or networking falls behind. It drops frames instead of building a queue, which favors a current image over complete visual history. That design is sensible for interactive input, but it means the stream is not a durable recording. The README does not document offline viewing, recording, or playback.

Clipboard transfer is optional through Share Clipboard. Text copied on the Mac can be pasted on the device, and Paste in Sill can send text copied on the device to the Mac. The documentation says Sill does not read the device clipboard by itself, and clipboard items marked as concealed by a password manager remain on the Mac.

Sill installation and first pairing

The README provides a signed, notarized Mac download and a Homebrew cask. Install the Mac app with the documented command. The mobile app is available from the App Store for iPhone and iPad.

The Homebrew command installs the same download from Sill's own tap:

brew install --cask saffsanity/sill/sill

After installing both apps, open Sill for Mac and the Sill app on the iPhone or iPad. The device needs Local Network access to find the Mac nearby. The Mac requests Screen Recording for capture, Accessibility for input and window actions, and Local Network on macOS 15 or later. The device can scan the Mac's pairing code with the camera, or the code can be typed. Over USB, the README says the device pairs by itself.

The documented connection choices are the same local network, a USB cable, Direct Wireless Connection when the devices share no network, or the user's own VPN with Remote Access enabled. For a first nearby connection, keep the devices on the same network, grant the listed permissions, then select the Mac from Sill's Connect to a Mac screen. The Mac's Devices settings list paired devices and allow an individual device to be removed.

Connection choices and the no-server boundary

Sill's connection design keeps the control point with the user. Bonjour discovery works on a local network. A USB connection is represented as Wired, while Direct Wireless Connection uses peer-to-peer Wi-Fi when the Mac and mobile device share no network. Direct Wireless Connection is off by default, so it must be enabled before it can serve as the fallback path.

For access away from the local network, Remote Access uses the user's own VPN, with Tailscale given as an example. The Mac must be reachable through that VPN, and Sill's Remote Access setting must be enabled. Sill does not describe an account-based relay or a hosted coordination service in the documented architecture.

The practical alternative is a conventional remote desktop session. Such a session generally presents a complete remote computer and commonly depends on a remote access service or its own connection setup. Sill instead focuses on selecting one Mac window, delivering a video stream, and translating mobile input into local Mac events. That difference may matter for privacy and control, but it also places the burden of reachability on the user's network and permissions.

Apple Pencil, trackpad and app-menu support

Sill does more than present a static screen. On iPad, a trackpad or attached mouse can scroll the window under the pointer. Apple Pencil acts as the pointer, while touch and taps provide direct manipulation. The on-screen trackpad, keys and momentum scrolling are part of the mobile interface, so the app can be used without a separate physical keyboard.

The Mac's input mapping includes three-finger swipes and pinches for Mission Control, App Exposé, Spaces, Apps and Show Desktop, using the keyboard shortcuts configured on the Mac. The README also describes reaching application menus. On iPadOS 26 or later, the iPad can show them in its own menu bar. On other layouts, a Menus button in Sill's bar exposes them. Sill for Mac reads each menu from the application and chooses the selected item through Accessibility. When someone moves the physical Mac mouse, the pointer position is shown on the mobile device.

These features depend on macOS application behavior and the accessibility mappings available on the Mac. The documentation does not claim compatibility with every menu, custom drawing surface, secure input field, or application-specific shortcut. The relevant limitation is not lack of input types, but reliance on macOS permission-controlled event translation.

Permissions, compatibility and maintenance

The system requirements are narrow and concrete. Sill requires a Mac with Apple silicon running macOS 14 or later. The iPhone or iPad must run iOS 17 or iPadOS 17 or later. On macOS 15 and later, Local Network permission is also required. The mobile app asks for Local Network access, and the camera is used for scanning a pairing code, with typed entry available as an alternative.

These requirements rule out Sill for Intel Macs, older macOS installations and older iOS or iPadOS versions. Screen Recording and Accessibility are not incidental permissions. Without Screen Recording, the selected window cannot be shown. Without Accessibility, the Mac cannot reliably translate taps, clicks, scrolls, keys and window commands into local events. A deployment that denies these prompts will not provide the complete advertised workflow.

The repository is not archived. Its last push was on 2026-10-15. Recent releases include Sill 0.5.1 on 2026-10-09, Sill 0.4.0 on 2026-09-28 and Sill 0.3.1 on 2026-09-27. The repository uses the Apache-2.0 license. The README does not specify a formal upgrade policy or compatibility policy for older releases, so an adopter should check release notes and permissions after each upgrade.

Where Sill is the wrong tool

Sill is the wrong choice when the goal is unattended administration, cross-platform access from Windows or Android, or a guaranteed stream that must preserve every frame despite network delay. It is also a poor fit for a user who cannot grant Screen Recording and Accessibility to the Mac app. Its documented client devices are iPhone and iPad, and its host requirements specifically name Apple silicon and recent Apple operating systems.

The dropped-frame policy creates another boundary. If the required use is recording or reviewing an exact sequence of events, Sill's live stream should not be treated as a recording system. The README describes no recording, export or replay workflow. Likewise, the documentation does not promise operation when the Mac is asleep, the user is not present to approve a macOS permission prompt, or the network path does not expose the Mac through the user's VPN.

For a user who only needs to inspect an occasionally used Mac window, Sill can be a focused choice because it avoids an account and a Sill-operated intermediary. For broader device support, centralized administration, or archival media, a different tool with those documented capabilities is the more suitable category.

Editorial conclusion

Sill suits Mac owners who want to reach an individual window from an iPhone or iPad without routing the session through a Sill account or server. It is less suitable for non-Apple Macs, older Apple operating systems, or people who need unattended access without granting Screen Recording and Accessibility permissions. Verify first that the Mac has Apple silicon and macOS 14 or later, the mobile device has iOS 17 or iPadOS 17 or later, and the intended connection path is available.

Frequently asked questions

Official sources

1. License: Apache-2.0
2. Project website
3. README
4. Releases
5. Saffsanity/sill on GitHub