SecondGlowPress and reviewers
Writing about SecondGlow, or filming it?
Write to support@secondglow.app and I’ll send you a free license the same day. I’m Jakub, I make SecondGlow on my own, and I’m glad to answer anything, on record.
In one sentence
SecondGlow turns a 2015 to 2020 Retina iMac into a monitor for a Mac with Apple silicon over one USB or Thunderbolt cable, at the panel’s full 5K or 4K, for $39 once.
The facts
- Price: $39 once, tax included. 7-day free trial with no account and no card. 14-day refund.
- One license: up to 7 of your own Macs. Free on any number of iMacs.
- Your Mac: any Mac with Apple silicon, M1 to M5, on macOS Ventura or later.
- The iMac: 27-inch 5K (late 2015, 2017, 2019, 2020), iMac Pro (2017), or 21.5-inch Retina 4K (2015, 2017, 2019), on macOS Monterey or later.
- Cable: USB-C to USB-A with USB 3 on every supported iMac, or Thunderbolt or USB4 on 2017 and later. No dongle, no hardware unit.
- Picture: the panel’s native resolution. Lossless while the screen is still, compressed on the GPU while it moves. About 50 to 60 fps on full-screen 5K video over USB 3, measured by me.
- Also: Mirror or Extend, sound through the iMac’s speakers (macOS Sonoma 14.2 or later), iMac brightness from your Mac, works with the laptop lid closed, encrypted link.
- One app: the same download on both Macs. It knows which one it’s on.
- Not in it: Intel Macs can’t send the picture, there’s no wireless mode, and the iMac’s camera, microphones, keyboard and mouse aren’t passed to your Mac.
How it compares
I keep a fair, sourced comparison with each alternative, including where the other one is the better choice: RetinaRelay, Luna Display, OpenDisplay (free), a new Studio Display, and every way to use a 5K iMac as a monitor.
Pictures
Free to use in articles and videos about SecondGlow.
Who makes it
Jakub Chalmovsky, Bratislava, Slovakia. SecondGlow launched on 3 November 2026 and is sold by Good Software s. r. o.