Encore vs the alternatives.
For an old iMac as a monitor.
Every realistic route, with what each maker lists, checked on 9 November 2026. Each name links to a full comparison with sources.
A Late 2009 or 2010 iMac, or one from 2007 to Early 2009: Encore is the app whose stated range reaches it. A 27-inch 5K iMac on a cable, at native 5K: RetinaRelay or Luna Display. A published latency figure: Second Display. Free: DeskJoin Screen on macOS 12.3 or later, or AirPlay on a 2019 or 2020 iMac. The iMac's keyboard and mouse working for your Mac over a cable, plus a smart display after work: Encore.
Side by side.
Each maker's own requirements and claims. Speeds are the makers' figures, not measured independently.
| Option | Price | Your Mac needs | Oldest iMac | Connection | Picture and speed | Extras |
|---|---|---|---|---|---|---|
| Encore | Free during the public beta | macOS 14 or later | Late 2009 (macOS 10.13); 2007 to Early 2009 with Receiver Legacy | Wi-Fi, Gigabit Ethernet, Thunderbolt | Sharp, lossless picture over a cable; Wi-Fi always lower quality; Ultra with ProRes 4444 over a cable; Retina iMacs at up to 2560 x 1440; latency not published yet | The iMac's keyboard and mouse over a cable; speakers; StandBy clocks, AirPlay music, Hey Mac |
| Second Display | $39 once (Pro $59); 7-day trial | macOS 14 or later, or Windows 11 | Late 2015 or later; Late 2012 to Mid 2015 with its free Connect app | Thunderbolt (lossless), Wi-Fi, Ethernet, USB-C | About 9 ms over Thunderbolt in its own test on a 24-inch M1 iMac | iMac's speakers, microphone and camera |
| RetinaRelay | $49 once; 7-day trial | macOS 13 or later | Late 2012 (macOS 10.15 or later) | Thunderbolt, USB, Gigabit Ethernet; Wi-Fi as a slower option | Up to native 5K at 60 fps (maker's claim); no latency figure | iMac's speakers |
| Luna Display | $89.99 USB-C dongle | macOS 10.13 or later, USB-C port | "Most iMacs from 2011 onward" | USB, Ethernet, Wi-Fi, Thunderbolt | Native 5K with the USB-C unit; maker states 1 to 4 ms wired, 7 to 25 ms Wi-Fi | Also iPads and Windows PCs |
| Duet Display | From $39.99 a year (US App Store) | macOS 11 or later, older build for 10.13 to 10.15 | Not stated | Wi-Fi; Thunderbolt between two Macs on macOS 12.3 or later | "60 frames per second with zero lag" (maker's claim) | Also iPads, Android, PCs |
| MacDisplay | €29.99 + VAT once for 3 Macs; free tier in 10-minute blocks | macOS 12.3 or later | 2014 (macOS 11 or later) | Thunderbolt 3 or later, Gigabit Ethernet, Wi-Fi | Native resolution; its own Ethernet clock tests show about 70 to 80 ms | Keyboard and mouse sharing; file transfer |
| DeskJoin Screen | Free, no account | macOS 12.3 or later | Any iMac on macOS 12.3 or later (about Late 2015) | Wi-Fi, Ethernet, Thunderbolt Bridge | No claims | None listed |
| Yam Air Desk | $7.99 once after a 7-day trial | macOS 10.10 or later | Late 2012 (macOS 10.15 or later) | Wi-Fi, Ethernet | 30 or 60 fps; no latency figure | Extend or mirror |
| TargetBridge | Free, open source | macOS 14 or later | Prebuilt receiver: macOS 14 on Intel (2019 to 2020 iMacs) | Thunderbolt Bridge; network link experimental | Up to 5K streams, 5K 60 fps marked experimental | None listed |
| Deskreen | Free, open source | Mac, Windows or Linux | Any device with a web browser | Wi-Fi | Needs a virtual display tool for an extended desktop | Any browser as a screen |
| AirPlay to Mac | Free, built in | macOS 12 or later | 2019 (macOS 12 or later) | Your network, no direct cable | "A much slower connection" (MacMost) | None |
| Target Display Mode | Free, built in | A Mac from 2019 or earlier, macOS 10.15.8 or earlier | 2009 to Mid 2014, iMac on macOS High Sierra or earlier | Mini DisplayPort or Thunderbolt | The iMac's panel at native resolution | None; not with a Mac from 2020 or later |
| Sidecar | Free, built in | macOS 10.15 or later | iPads only, not iMacs | Wireless, or USB | Not an option for an iMac | Apple Pencil on iPad |
| HDMI capture card | About $20 plus a cable | Any HDMI output | macOS 14 for the app 9to5Mac uses (2019 and 2020) | HDMI via USB | Limited by the card | Works from any HDMI source |
| Driver board | $449 kit on one Australian store | Any video source | 27-inch iMac, panels vary; the computer is removed | USB-C on the 5K kit | 5120 x 2880 at 60 Hz on the 5K kit | No macOS, camera or speakers left |
Checked on 9 November 2026 on each maker's own page. Every comparison links to its sources. Wrong or out of date? Tell us and we fix it.
Where Encore wins.
And where it doesn't.
Where Encore wins
- The oldest iMacs. Every Intel iMac from Late 2009 to 2020, and 2007 to Early 2009 with Encore Receiver Legacy. Of the apps that name an oldest iMac, Encore's range starts earliest. Luna Display says most iMacs from 2011; the rest start at Late 2012 or later.
- The whole iMac, over a cable. The iMac's own keyboard and mouse control your Mac, and its speakers play your Mac's sound. Several iMacs at once.
- A smart display after work. StandBy with clock faces, weather and your calendar, AirPlay music on a turning record, and Hey Mac. None of the others lists anything like it.
- Low cost and simple. Encore is free during the public beta, with no account and no dongle.
- Built for text and privacy. Its own encrypted protocol, lossless tiles over a cable, Ultra with ProRes 4444 over a cable. No Encore server.
Where Encore is weaker
- No native 5K. Retina iMacs are sent at up to 2560 x 1440. RetinaRelay, Luna Display and TargetBridge state native 5K.
- No published latency yet. Second Display and Luna Display publish figures from their own tests. We will publish ours per iMac model once measured.
- Wi-Fi is always lower quality than a cable, and the iMac's keyboard and mouse need a cable.
- Your Mac needs macOS 14 or later. RetinaRelay accepts 13, MacDisplay and DeskJoin 12.3, Luna Display 10.13.
- Mac to Mac only. No PC host, no iPad. Luna Display and Duet do both.
- macOS asks once before it opens the app. The install guide shows the clicks.
Where each one wins.
Every option here is the right pick for someone. Click through for the full comparison.
Second Display
Lossless over Thunderbolt, about 9 ms in its own test, a Windows version, and the iMac's speakers, microphone and camera. iMacs from before Late 2012 are out.
Pick it for a Late 2015 or newer iMac on Thunderbolt.
RetinaRelay
Built for 5K over a cable: native 5K at 60 fps claimed, one host Mac and unlimited iMacs.
Pick it for a 27-inch 5K iMac at native resolution.
Luna Display
A dongle by Astropad: native 5K with the USB-C unit, from 2011, and PC hosts and iPads too.
Pick it for native 5K, if $89.99 of hardware is fine.
Duet Display
One subscription for iPads, Android tablets, PCs and Macs. It states no oldest iMac.
Pick it for a tablet as a screen as well.
MacDisplay
Native resolution, a host Mac from macOS 12.3, and a free tier in 10-minute blocks.
Pick it for a 2014 or newer iMac and a Mac that can't run macOS 14.
DeskJoin Screen
Free with no account, for iMacs that run macOS 12.3 or later.
Pick it for free, on a newer iMac.
Yam Air Desk
The lowest-priced paid app we found, over Wi-Fi or Ethernet.
Pick it for the lowest price on a 2012 or newer iMac.
TargetBridge
Free and open source, up to 5K over Thunderbolt Bridge, for iMacs on macOS 14.
Pick it for a 2019 or 2020 iMac and a free route.
Deskreen
Free and open source, any browser as a screen, over Wi-Fi.
Pick it for a quick, free screen in a browser.
AirPlay to Mac
Free and built in, on iMacs from 2019 with macOS 12 or later.
Pick it for a 2019 or 2020 iMac, now and then.
Target Display Mode
A real monitor signal over a cable, for free, with a Mac from 2019 or earlier on Catalina and an iMac from 2009 to Mid 2014.
Pick it for an Intel Mac still on Catalina.
Sidecar
A free second screen on a compatible iPad. Not for an iMac.
Pick it for an iPad you already own.
HDMI capture card
About $20, works from any HDMI source, viewer app on the iMac.
Pick it for a game console or camera on the iMac.
Driver board
Replaces the computer inside a 27-inch iMac with a monitor board. Native 5K, but the iMac stops being a computer.
Pick it for a dead iMac with a good panel.
Questions
Which app is right for my old iMac?
It depends on your iMac's year and what you need. For a Late 2009 or 2010 iMac, Encore is the app whose stated range reaches them (2007 to Early 2009 with Encore Receiver Legacy). From 2011, Luna Display also works, with a $89.99 dongle. For native 5K on a 27-inch Retina iMac, RetinaRelay or Luna Display fit better. If you want a published latency figure, Second Display reports about 9 ms over Thunderbolt in its own test.
Does Target Display Mode still work?
Only with a Mac from 2019 or earlier on macOS Catalina 10.15.8 or earlier, according to Apple, with an iMac from 2009 to Mid 2014 on High Sierra or earlier. It does not work with any Mac with Apple silicon, or with a Retina 5K iMac. The full rules: Encore vs Target Display Mode.
Can a 2011 iMac be a second screen for an M3 MacBook?
Yes, with Encore. Install Encore Receiver on the 2011 iMac and Encore on the MacBook (macOS 14 or later), then connect over Wi-Fi, Gigabit Ethernet or Thunderbolt. Target Display Mode can't, because Apple requires a Mac from 2019 or earlier. Luna Display also supports 2011 iMacs, with a dongle.
Is Encore secure?
Encore uses its own protocol and encrypts everything it sends with ChaCha20-Poly1305 and keys agreed with X25519. There is no unencrypted fallback. A Mac pairs only with the code shown on the iMac, and everything goes straight between your Mac and the iMac: no account, no Encore server.
How much does Encore cost?
Encore is free during the public beta. For comparison, on 9 November 2026: Second Display $39 once, RetinaRelay $49 once, MacDisplay €29.99 plus VAT, Luna Display $89.99 for its dongle, Duet from $39.99 a year, and Yam Air Desk $7.99. DeskJoin Screen, Deskreen, TargetBridge and AirPlay to Mac are free. Public beta
Which option gives native 5K on a 5K iMac?
Luna Display (with its USB-C unit), RetinaRelay and TargetBridge state it, and a driver board gives native 5K by removing the computer. Encore sends Retina iMacs at up to 2560 x 1440. Every 5K route compared.
Is there a free way to use an old iMac as a monitor?
DeskJoin Screen is free on iMacs with macOS 12.3 or later, AirPlay to Mac is built into iMacs from 2019, TargetBridge is free and open source for iMacs that run macOS 14, and Target Display Mode is free with a Mac from 2019 or earlier on Catalina. Encore is free during the public beta.
More detail, with hardware routes too: every way to use an old iMac as a monitor. Your model: compatibility and cables. Stuck? Help center.