SecondGlowComparison · checked on 13 November 2026
SecondGlow vs RetinaRelay for a 5K iMac
These two are close. Both turn a 5K iMac into a display over a cable, both compress the picture on the GPU instead of sending a video stream, and both have a 7-day trial and a 14-day refund. Both play sound through the iMac. The differences are Intel support, price, how many Macs one license covers, and setup: RetinaRelay is two apps, Host and Viewer, and SecondGlow is one app for both Macs.
Choose RetinaRelay if you have an Intel Mac or an iMac older than 2015.
Choose SecondGlow if you have an Apple silicon Mac and want the same sharp 5K for less, from one app on both Macs, on up to seven of your Macs, with an encrypted link and iMac brightness from your Mac.
| SecondGlow | RetinaRelay | |
|---|---|---|
| Price | $39 once, up to 7 of your Macs | $49 once, for one Host Mac (source) |
| Apps | One app, the same download on both Macs | Two apps: Host on your Mac, Viewer on the iMac (source) |
| Free trial · refund | 7 days · 14 days | 7 days · 14 days (source) |
| Your Mac | Apple silicon, macOS Ventura or later | Apple silicon or Intel, macOS Ventura or later (source) |
| The iMac | Retina iMac, 2015 to 2020 (27-inch 5K or 21.5-inch 4K), macOS Monterey or later | Late 2012 or newer, macOS Catalina or later (source) |
| Cables | One cable: USB-C to USB-A (USB 3), or Thunderbolt on 2017 and later iMacs | USB 3 (Apple silicon Host), Thunderbolt or Ethernet; Wi-Fi as a fallback (source) |
| 5K | Native 5120 × 2880. About 50 to 60 fps on full-screen video over USB 3, measured by me | Native 5K at 60 fps, per its site (source) |
| Sound on the iMac | Yes, on macOS Sonoma 14.2 or later; macOS asks once for System Audio Recording | Yes, after installing an audio device once with your admin password (source) |
| Laptop lid closed | Yes, on battery too | Yes, on power (source) |
| Link between the Macs | Encrypted | Not encrypted; its FAQ notes it runs over a direct cable between your two Macs (source) |
Where RetinaRelay is better
- Intel Macs. An Intel Mac can be the Host (over Thunderbolt or Ethernet). SecondGlow needs Apple silicon.
- More iMacs. It supports iMacs from late 2012 on Catalina, so the 2014 5K iMac too.
- More connections. Ethernet and Wi-Fi as well as USB and Thunderbolt.
Where SecondGlow is better
- One app. Download the same SecondGlow on both Macs and open it: it knows which Mac it’s on. No choosing between a Host and a Viewer.
- Price. $39 instead of $49.
- More Macs per license. Up to 7 of your own Macs, not one.
- Encrypted link. The picture and sound are encrypted on the cable between your Macs.
- Nothing to install for sound. No extra audio device and no admin password.
- Lid closed, on battery. Close your laptop and keep working on the iMac, plugged in or not. RetinaRelay’s site says its closed-lid mode needs power.
- iMac brightness. A slider in SecondGlow on your Mac sets the iMac’s brightness. RetinaRelay’s FAQ says its Viewer has no brightness controls.
Which should you choose?
If you have an Intel Mac or an older iMac, choose RetinaRelay. If you have an Apple silicon Mac and a 2015 to 2020 5K iMac, SecondGlow does the same job for less and covers all your Macs. Both have a free trial, so you can try them on your own desk.
Still deciding? Every way to use a 5K iMac as a monitor, including free options.
Sources
Checked on 13 November 2026, on each product’s own site. Prices and features change; follow the links for today’s details.