ScreenHelm

ScreenHelm steers every display of your Mac from one place, in the menu bar and in a window with a page for each display. It is free and open source under the MIT license.

Key features

• Brightness on one slider, whatever is behind it: the backlight of an Apple display, a monitor's own setting over DDC, or software dimming for the rest. The keyboard's brightness and volume keys and an on-screen display work for the monitors macOS ignores
• XDR brightness past 100% on a MacBook Pro or Pro Display XDR, up to a limit you set, turning itself off on a low battery or a hot Mac
• Every resolution a display reports, including the ones System Settings hides, with favorites, a slider between larger text and more space, the refresh rate, HiDPI, the area beside the camera housing, rotation, HDR, reference presets and the color profile. More sharp sizes can be added to a display's own override file
• Picture adjustments: contrast, gamma, color temperature, gains, inverted colors, the number of color steps and dithering
• Brightness that follows the built-in display, by percentage or by nits, or the light in the room. Night Shift with its strength, True Tone and Dark Mode in the menu bar, and Night Shift and True Tone switched off while a display shows HDR if you like
• Arrangement: displays dragged into place with guide lines, an arrangement kept for each set of displays and put back when macOS changes it, a display switched off without pulling its cable, the main display and mirroring, Sidecar
• Virtual screens: a display with nothing plugged in, from a template or in the shape of a real one
• Picture in picture: a live copy of a display or a window in a floating window or across another display, turned, mirrored, cropped by dragging over the display, filtered, with a .cube lookup table, in HDR on macOS 15 and later, with the pointer hidden over the display it covers
• Display groups with a rule for when they are active, one slider for all of them, and text kept the same size on their displays when one changes resolution
• When displays come and go: run a Shortcut, open a file, or keep the Mac awake while a chosen display is connected
• Shortcuts you record (none is set until you do), actions for the Shortcuts app, and, once you turn them on, the command line, screenhelm:// links and HTTP on your own Mac
• A menu bar panel with the everyday controls for each display: brightness, volume, resolution, refresh rate, input, preset, HiDPI, XDR, and a menu to rotate a display, make it the main one, mirror it or switch it off
• Export and import of the settings, ScreenHelm's own log in a window, and a diagnostic report without serial numbers
• Light, dark or system appearance, English and Vietnamese, Sparkle updates

A way back

• A change that could leave a display unusable has to be kept within 15 seconds or it is undone, and a new mode is written for good only once kept
• Control-Option-Command-Escape drops everything ScreenHelm has applied
• Opened with Shift held, or after a start that ended while it applied settings, it applies nothing saved
• Software dimming never comes back darker than 15% by itself, and nothing is ever written to a display's EDID
• Quitting switches back on every display ScreenHelm switched off, also through a small watcher if the app is killed

Private by design

• No account, no telemetry, no analytics. The only network request is the update check to updates.dangkhoabach.vn, which can be turned off
• A display's serial number stays hidden until you ask to see it, and out of the logs and the diagnostic report
• A picture in picture is drawn straight from the screen and never written to disk
• Display commands from the command line and from links are off until you turn them on; the HTTP server listens on this Mac only and every request needs a token kept in your login Keychain

Requirements and limits

• macOS 14 Sonoma or later, Apple Silicon or Intel. Controlling a monitor over DDC needs Apple Silicon; docks, adapters and TVs often don't pass it on, and DisplayLink never does
• Changing displays needs no permission. Accessibility is asked for the keyboard's keys, Screen Recording for picture in picture, and an administrator's password each time the file for more resolutions is installed or removed
• Features that need hardware other than a MacBook Pro's own display are marked Experimental until they have run on it
• Software dimming and the picture adjustments last while ScreenHelm runs. Another app that changes the same color table, such as BetterDisplay, MonitorControl, Lunar or f.lux, and ScreenHelm undo each other: use one at a time

Good to know

• The app is signed with an Apple Development certificate and not notarized: open it the first time from System Settings › Privacy & Security › Open Anyway