How can you "force" or "hack" the iMac Retina 4K and iMac Retina 5K models to run at native resolution or otherwise fit more content on screen than by default?

The Retina 5K iMac models from the "Late 2014," "Mid-2015," "Late 2015," "Mid-2017," "2019" and "2020" lines all have a 5120x2880 native resolution, but by default run "pixel doubled" at a setting that looks like 2560x1440, it just has four times the detail of a "traditional" display.

The Retina 5K iMac models:

• iMac "Core i5" 3.5 27-Inch (5K, Late 2014)
• iMac "Core i7" 4.0 27-Inch (5K, Late 2014)
• iMac "Core i5" 3.3 27-Inch (5K, Mid-2015)
• iMac "Core i5" 3.2 27-Inch (5K, Late 2015)
• iMac "Core i5" 3.3 27-Inch (5K, Late 2015)
• iMac "Core i7" 4.0 27-Inch (5K, Late 2015)
• iMac "Core i5" 3.4 27-Inch (5K, Mid-2017)
• iMac "Core i5" 3.5 27-Inch (5K, Mid-2017)
• iMac "Core i5" 3.8 27-Inch (5K, Mid-2017)
• iMac "Core i7" 4.2 27-Inch (5K, Mid-2017)
• iMac "Core i5" 3.0 27-Inch (5K, 2019)
• iMac "Core i5" 3.1 27-Inch (5K, 2019)
• iMac "Core i5" 3.7 27-Inch (5K, 2019)
• iMac "Core i9" 3.6 27-Inch (5K, 2019)
• iMac "Core i5" 3.1 27-Inch (5K, 2020)
• iMac "Core i5" 3.3 27-Inch (5K, 2020)
• iMac "Core i7" 3.8 27-Inch (5K, 2020)
• iMac "Core i9" 3.6 27-Inch (5K, 2020)
• iMac "Core i7" 3.8 27-Inch (5K, 2020; 5700/XT)
• iMac "Core i9" 3.6 27-Inch (5K, 2020; 5700/XT)

The smaller Retina 4K iMac models from the "Late 2015," "Mid-2017" and "2019" lines have a 4096x2304 native resolution, but by default run "pixel doubled" at 2048x1152.

The Retina 4K iMac models:

• iMac "Core i5" 3.1 21.5-Inch (4K, Late 2015)
• iMac "Core i7" 3.3 21.5-Inch (4K, Late 2015)
• iMac "Core i5" 3.0 21.5-Inch (4K, Mid-2017)
• iMac "Core i5" 3.4 21.5-Inch (4K, Mid-2017)
• iMac "Core i7" 3.6 21.5-Inch (4K, Mid-2017)
• iMac "Core i3" 3.6 21.5-Inch (4K, 2019)
• iMac "Core i5" 3.0 21.5-Inch (4K, 2019)
• iMac "Core i7" 3.2 21.5-Inch (4K, 2019)

Default Display Options

The "Retina 5K" iMac display looks best at the default 2560x1440 setting and likewise the smaller "Retina 4K" iMac display looks best at its default 2048x1152 setting.

However, Apple also provides four other scaled options ranging from "Larger Text" to "More Space" by default.

Photo Credit: EveryMac.com (Standard iMac Retina 5K Display Settings)

To access these settings, select "System Preferences" under the Apple Menu and then click the "Displays" icon.

These scaled options on the iMac "Retina 5K" look like the following resolutions on a "traditional" display:

Larger Text		Best (Retina)		More Space
1600x900	2048x1152	2560x1440	2880x1620	3200x1800

The scaled resolutions are not of the same visual quality as the default "Retina" setting -- which has enough clarity that the individual pixels cannot be differentiated by most people -- but these scaled resolutions still offer sufficient visual quality for many purposes.

Photo Credit: EveryMac.com (Additional iMac Retina 5K Resolution Options)

You also can "press and hold the 'Option' key while clicking the 'Scaled' button" in the "Displays" Control Panel to see additional resolutions.

Third-Party Apps for More Display Options

For even more control, there are at least three third-party "hacks" available to provide other options that may be of interest. More control may be useful for some games, in particular.

Of course, Apple does not support third-party hacks. Should you choose to proceed with unofficial methods, be absolutely sure to backup your entire computer first. It's a good idea to backup your computer regularly even if you don't use hacks, naturally.

Retina DisplayMenu

Retina DisplayMenu (direct download link) is free from the "phoenixdev" Reddit user. Originally created for the Retina Display MacBook Pro models, this simple utility adds Apple's supported resolutions in addition to several other ones to the menu bar and makes switching between them easy. It is a 32-bit app, so it does not work with iMac models running versions of the macOS past macOS Mojave (10.14).

QuickRes

QuickRes, which is highly regarded, is the self-described "quickest and easiest way to switch between screen resolutions on your Mac." It has been updated specifically to support the iMac Retina 5K models. The latest version requires OS X El Capitan (10.11) or higher and costs US$14.99.

SwitchResX

Finally, the sophisticated SwitchResX shareware application offers extensive control over "Monitor Resolution, Color Depth, Video Mirroring, Display Rotation, Display Overscan" and more. It even allows one to create and enable new resolutions.

Versions of SwitchResX are compatible with several revisions of Mac OS X and even Mac OS 9. The app is offered with a free ten day trial, and costs an entirely reasonable €14 to register.

iMac Retina 4K & Retina 5K Resolutions Summary

Ultimately, the Apple provided options should be sufficient for most users, but for those who find more control valuable, Retina DisplayMenu, QuickRes and SwitchResX can be welcomed, also.

If you find QuickRes or SwitchResX useful, EveryMac.com strongly encourages registering the software to support continued development.