magnify

TL;DR

A magnifying glass that follows your cursor anywhere on macOS. Perfect if you need to pinpoint stuff while screen sharing.

To install, run this in your terminal:

brew trust robert-bogos/magnify && brew install robert-bogos/magnify/magnify

To use, run this in your terminal:

magnify

Requirements

• macOS 13+ (Apple Silicon).
• Xcode not required — builds with Command Line Tools using swiftc. (swift build / swift test need full Xcode; the scripts below use swiftc.)

Install

brew trust robert-bogos/magnify && brew install robert-bogos/magnify/magnify

The trust step is a one-time grant Homebrew requires for third-party taps (this repo isn't in Homebrew's official cask index) — doing it first means install taps and installs in one shot instead of failing and asking you to retry.

Magnify is ad-hoc signed, not notarized by Apple — the cask automatically clears the Gatekeeper quarantine flag on install, so no separate "right-click ▸ Open" workaround is needed. You'll still need to grant Screen Recording permission on first launch (see below).

Upgrade later with brew upgrade --cask magnify.

Build from source

./scripts/build.sh

Compiles, assembles Magnify.app, and ad-hoc signs it.

Run

./magnify --zoom 2 --size 320

./magnify launches Magnify.app via LaunchServices (open -n) so it gets its own identity in the permission lists. It runs in the background — quit it from the 🔍 icon in the menu bar, or killall magnify.

First launch: grant Screen Recording

The first run triggers a Screen Recording permission prompt. Until it's granted, no lens is shown (so it can't block you from clicking) — the 🔍 menu bar reads "Waiting for Screen Recording permission…". Enable it here:

System Settings ▸ Privacy & Security ▸ Screen Recording ▸ enable Magnify

The lens then appears on its own within ~2s — no relaunch needed.

If Magnify doesn't appear in the list, force a clean prompt:

killall magnify 2>/dev/null; tccutil reset ScreenCapture com.rbogos.magnify
./magnify

Options

Flag	Default	Meaning
--zoom <n>	2	Magnification (1–20)
--size <pt>	300	Lens side length in points (100–800)
--shape <s>	square	square or circle
--fps <n>	60	Capture frame rate (15–120)
--filter <f>	nearest	nearest (crisp pixels) or linear (smooth)
--flip-y	off	Flip vertical sampling — rarely needed (see Troubleshooting)
-h, --help		Show help

Controls

• Quit: Ctrl-C in the terminal (always works).
• Show / hide the lens: ⌃⌥M, or the 🔍 menu-bar item. Hiding stops capture so it idles cheaply. Neither needs any extra permission.
• Live zoom / resize / Esc-to-quit: need Accessibility permission (System Settings ▸ Privacy & Security ▸ Accessibility ▸ enable Magnify). Then: scroll or +/- to zoom, [ / ] to resize, Esc to quit.

How it works

• A borderless, transparent, click-through NSWindow at the shielding window level floats above everything and is excluded from capture (sharingType = .none), so it never captures itself (no "hall of mirrors").
• ScreenCaptureKit streams the display the cursor is on; the latest frame is stored as a CGImage.
• A CVDisplayLink drives a per-frame update: the frame is set as a CALayer's contents and a normalized contentsRect (computed in MagnifyCore/Geometry) selects the region under the cursor, which the layer scales up — GPU-cheap, no per-frame CPU cropping.
• Crossing to another monitor rebuilds the stream for that display.

Test

./scripts/test.sh   # geometry checks via swiftc (no Xcode needed)

The same assertions live in Tests/MagnifyCoreTests/ for swift test once Xcode is installed.

Troubleshooting

• No lens appears: Screen Recording isn't granted yet — the lens stays hidden until it is. Grant it (see above) and the lens shows up within ~2s; the 🔍 menu bar shows current status.
• "Magnify" isn't in the Screen Recording list: it only shows up once it has requested capture and was launched via open (the ./magnify wrapper does this). Running the raw binary from a shell attributes the request to your terminal app instead. If it's still missing, run tccutil reset ScreenCapture com.rbogos.magnify then ./magnify.
• Lens pans vertically the wrong way (moving the cursor up shows lower content): your setup samples top-down — run with --flip-y.
• Scroll / keyboard controls do nothing: grant Accessibility (see Controls). Ctrl-C still quits regardless.
• Re-prompted for Screen Recording after rebuilding — or the toggle is on but the lens never appears: ad-hoc signatures change on every rebuild, so macOS stops honoring the old grant. Reset it and grant once more: tccutil reset ScreenCapture com.rbogos.magnify, then run ./magnify again. (You only hit this if you rebuild; a build-once install grants once and stays put.)