How do I install the Set Display skill?

Run npx skillmds@latest add pabasara-mahindapala/set-display in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

Is Set Display safe to use?

This skill has not completed SkillMD's automated safety review yet. SkillMD never runs a skill's scripts for you; review the SKILL.md before installing.

Which AI agents work with Set Display?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is Set Display free to use?

Yes. Installing skills from SkillMD is free, and the skill stays under its author's original license.

Who published Set Display?

pabasara-mahindapala (@pabasara-mahindapala) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Set Display by pabasara-mahindapala

Name: Set Display
Author: pabasara-mahindapala

Set Display

Set the resolution and refresh rate of an external display on macOS via CoreGraphics, including modes that System Settings refuses to list. Use when a monitor is stuck at the wrong resolution or aspect ratio, when an ultrawide shows only 16:9 options, when the desired refresh rate is missing, or when the user wants to enumerate every mode a display actually supports. Keywords: display resolution, refresh rate, ultrawide, 3440x1440, hz, monitor stuck, wrong resolution, show all resolutions, aspect ratio, external monitor, EDID.

File contents

Set Display Mode

Set macOS display modes directly through CoreGraphics, bypassing the System Settings UI.

Why this exists

The Displays pane filters its resolution list to the aspect ratio it derives from the display's EDID preferred timing. When a hub or adapter advertises a preferred timing that does not match the panel (e.g. 1920x1080 on a 3440x1440 ultrawide), macOS hides every mode of the real aspect ratio. Toggling "Show all resolutions" does not help — that toggle adds low-resolution variants, it does not lift the aspect-ratio filter.

The modes are still present and fully usable in CoreGraphics. These tools reach them.

Tools

Both live in tools/ beside this file. Use absolute paths when invoking them.

tool	usage
`listmodes`	no arguments — prints every mode of the first external display, marks the current one
`setmode`	`setmode <width> <height> <refresh>` — applies that mode permanently

If a binary is missing or fails to run, rebuild it in tools/:

swiftc -O setmode.swift -o setmode
swiftc -O modes.swift -o listmodes

Procedure

Enumerate first. Run listmodes and read the actual list. Never guess a mode — setmode exits non-zero with mode WxH@R not available if it is not offered.
Read the output correctly. Each line shows point size, backing pixels, and refresh:
```
3440x1440   backing  3440x1440    99.00Hz              <- native, use this
1720x720    backing  3440x1440    99.00Hz HiDPI        <- UI renders huge, rarely wanted
```
setmode only matches native modes where point size equals backing size, so the HiDPI variants are not reachable through it by design.
Apply the lowest safe refresh first, confirm the display survives, then step up. The mode list reflects what the EDID advertises, not a guarantee the cable or hub sustains the bandwidth. An unsustainable mode gives a black screen.
Verify with listmodes again, or independently:
```
system_profiler SPDisplaysDataType | grep -A5 "<display name>"
```
Immediately after a change, setmode may print a placeholder size such as 1x1 while the link renegotiates. That is not a failure — re-query to get the settled value.

Recovery

A mode that the hardware cannot sustain blanks the screen. Unplug and replug the display cable; macOS falls back to a safe mode. Warn the user before applying a refresh rate that has not been confirmed working, so they can be at the machine to do this.

Scope and limits

Targets the first non-builtin display only. With two or more external monitors it will pick whichever CoreGraphics enumerates first, which may not be the intended one. Extend setmode.swift to select by display ID if that case comes up.
Changes are applied with .permanently, so they persist across reboots and replugs.
The mode stays absent from the System Settings list — this sets the mode, not the UI filter.
Refresh rate ceilings are a link property. If the desired rate is not in listmodes at all, no software can add it; that needs a different cable, port, or a direct connection instead of a hub.

---name: set-displaydescription: Set the resolution and refresh rate of an external display on macOS via CoreGraphics, including modes that System Settings refuses to list. Use when a monitor is stuck at the wrong resolution or aspect ratio, when an ultrawide shows only 16:9 options, when the desired refresh rate is missing, or when the user wants to enumerate every mode a display actually supports. Keywords: display resolution, refresh rate, ultrawide, 3440x1440, hz, monitor stuck, wrong resolution, show all resolutions, aspect ratio, external monitor, EDID.---# Set Display ModeSet macOS display modes directly through CoreGraphics, bypassing the System Settings UI.## Why this existsThe Displays pane filters its resolution list to the aspect ratio it derives from thedisplay's EDID *preferred* timing. When a hub or adapter advertises a preferred timing thatdoes not match the panel (e.g. 1920x1080 on a 3440x1440 ultrawide), macOS hides every modeof the real aspect ratio. Toggling "Show all resolutions" does not help — that toggle addslow-resolution variants, it does not lift the aspect-ratio filter.The modes are still present and fully usable in CoreGraphics. These tools reach them.## ToolsBoth live in `tools/` beside this file. Use absolute paths when invoking them.| tool | usage ||---|---|| `listmodes` | no arguments — prints every mode of the first external display, marks the current one || `setmode` | `setmode <width> <height> <refresh>` — applies that mode permanently |If a binary is missing or fails to run, rebuild it in `tools/`:```swiftc -O setmode.swift -o setmodeswiftc -O modes.swift -o listmodes```## Procedure1. **Enumerate first.** Run `listmodes` and read the actual list. Never guess a mode — `setmode` exits non-zero with `mode WxH@R not available` if it is not offered.2. **Read the output correctly.** Each line shows point size, backing pixels, and refresh: ``` 3440x1440 backing 3440x1440 99.00Hz <- native, use this 1720x720 backing 3440x1440 99.00Hz HiDPI <- UI renders huge, rarely wanted ``` `setmode` only matches native modes where point size equals backing size, so the HiDPI variants are not reachable through it by design.3. **Apply the lowest safe refresh first**, confirm the display survives, then step up. The mode list reflects what the EDID advertises, not a guarantee the cable or hub sustains the bandwidth. An unsustainable mode gives a black screen.4. **Verify** with `listmodes` again, or independently: ``` system_profiler SPDisplaysDataType | grep -A5 "<display name>" ``` Immediately after a change, `setmode` may print a placeholder size such as `1x1` while the link renegotiates. That is not a failure — re-query to get the settled value.## RecoveryA mode that the hardware cannot sustain blanks the screen. Unplug and replug the displaycable; macOS falls back to a safe mode. Warn the user before applying a refresh rate thathas not been confirmed working, so they can be at the machine to do this.## Scope and limits- Targets **the first non-builtin display only**. With two or more external monitors it will pick whichever CoreGraphics enumerates first, which may not be the intended one. Extend `setmode.swift` to select by display ID if that case comes up.- Changes are applied with `.permanently`, so they persist across reboots and replugs.- The mode stays absent from the System Settings list — this sets the mode, not the UI filter.- Refresh rate ceilings are a link property. If the desired rate is not in `listmodes` at all, no software can add it; that needs a different cable, port, or a direct connection instead of a hub.

Frequently asked questions