What it is
Software-defined display reuse
Capture the sender desktop, encode it, transport it over a direct Thunderbolt network path, decode it on the receiver, and layer Dockstation behavior on top.
Official project hub
TargetBridge: use your old iMac as a 5K external display for Apple Silicon Macs
TargetBridge brings back the "use my iMac as a screen" workflow through a direct Mac-to-Mac software pipeline built around ScreenCaptureKit, VideoToolbox and Thunderbolt Bridge. It is free, open source, and now pushes further with Input Dockstation, Audio Relay and remote automation.
- Free and open source, no subscription and no dongle required.
- Direct Mac-to-Mac pipeline built around ScreenCaptureKit, VideoToolbox and Thunderbolt Bridge.
- Supports Intel or Apple Silicon receiver Macs, with Thunderbolt Bridge as the primary low-latency path.
- Documented download flow ships pre-built Sender and Receiver apps for Apple Silicon and Intel receiver Macs.
Definition
What is TargetBridge?
TargetBridge is a free, open-source macOS app that turns an old iMac into a low-latency 5K external display and input dock for an Apple Silicon Mac over Thunderbolt Bridge. It is not a data integration or ETL tool. The name overlaps with enterprise middleware, the product does not: this is a display-streaming utility for Macs.
Key benefits
Why use TargetBridge?
TargetBridge puts an idle iMac back to work as a 5K display and input dock, with no extra hardware to buy and no recurring cost. These are the practical reasons to pick it.
- Free of charge: every feature ships without a license fee.
- Open source: code, issues and releases are public on GitHub.
- No dongle: no proprietary accessory between the two Macs, just a Thunderbolt cable.
- No subscription: nothing recurring, nothing locked behind a paywall.
- Hardware reuse: an idle Intel iMac goes back to work as a 5K panel.
- Low latency over cable: Thunderbolt Bridge keeps the stream direct and fast.
Important clarification
TargetBridge is not native Target Display Mode.
TargetBridge is a low-latency Mac-to-Mac display stream using ScreenCaptureKit, VideoToolbox and Thunderbolt Bridge. It is not Apple's original TDM firmware feature, and saying that clearly avoids the most common setup misunderstandings.
Why this matters
A workspace bridge, not just an old-iMac workaround
TargetBridge is more than a display trick: it bridges display, input, audio, brightness and Thunderbolt networking extras in one low-friction setup.
Core features
More than a screen mirror.
TargetBridge 3.1 goes well beyond simple display mirroring. It now covers multi-receiver workflows, audio, input relay, remote brightness, automation and shared desk ergonomics in one Mac-to-Mac setup.
Display workflow
- Mirror mode and extended desktop mode
- Multiple receivers from one sender
- Automatic receiver discovery over Bonjour
- Saved extended-layout restore when reconnecting
Dockstation layer
- Input Dockstation with keyboard and mouse relay
- Clipboard sync tied to the active input master
- Remote brightness control from the sender
- Audio Relay for streamed system audio
Power-user extras
- Experimental Network Link transport over LAN
- Shared localization files for Sender and Receiver
- Manifest-based official addons
- Remote connection automation via URL scheme, CLI and SSH
Dockstation
Turn your old iMac into a display + input dock.
Dockstation is what turns the project from a display workaround into a practical desk workflow. It combines screen reuse with keyboard, mouse, clipboard, brightness and audio controls that matter every day.
Keyboard and mouse relay
Switch between "This Mac is Master" and "Receiver is Master" so one keyboard and mouse can stay inside the same TargetBridge session model.
Clipboard sync
Text clipboard sync follows the active input master so copy and paste feels like one workspace.
Remote brightness
The sender can adjust receiver panel brightness directly from the session UI.
Audio Relay
System audio can be streamed alongside video through the official addon path.
Thunderbolt networking extras
The same cable can also carry standard macOS services like file sharing, SSH, SFTP, Time Machine, printer sharing and Internet Sharing.
Automation hooks
A CLI wrapper, URL scheme, launch arguments and SSH recipes make it easier to reconnect or script multi-Mac setups.
Public benchmark board
Benchmarks: real 5K presets and latency notes
The benchmark page now shows the concrete presets already documented by the project, from 2560 x 1440 @ 60 up to 5120 x 2880 @ 48. Where the repo does not yet publish reproducible latency or load charts, the site keeps those fields clearly marked instead of guessing numbers.
The project docs already include a native 5K preset for 27-inch iMac setups.
If text clarity matters most, this is the preset people should look at first.
This is the smoother 60 fps profile currently documented by the project.
This is the safest 60 fps starting point before stepping up to 4K or 5K.
Comparison snapshot
TargetBridge vs AirPlay vs Luna Display
This comparison anchors on verified TargetBridge preset values and clear positioning notes. Same-hardware latency and system-load charts will be added as public test data lands.
| Metric | TargetBridge | AirPlay | Luna Display |
|---|---|---|---|
| Direct cable-first path | Yes. Thunderbolt Bridge is the primary path. | No. AirPlay is network-first. | Sometimes. Depends on Luna hardware and supported connection path. |
| Recurring cost | No. Free and open source. | No. Built into Apple platforms. | No subscription, but paid hardware is required. |
| Old iMac positioning | Built around reusing older Intel iMac displays. | AirPlay Receiver support is limited to newer Macs. | Broad compatibility, but it is still a paid accessory path. |
| 5K story | Official stream profiles go up to 5120 x 2880. | This site does not treat AirPlay as the 5K-first option. | Astropad markets full 5K iMac support. |
Cables and adapters
Recommended cables and adapters
The right cable avoids most setup problems. These are the project-documented starting points for future-proof cables and older Thunderbolt 2 setups.
OWC 0.8m Thunderbolt 5 Cable — OWCCBLTB5C0.8M
Documented by the project as a current starting point for compatible hardware setups.
OWC 1.0m Thunderbolt 5 Cable — OWCCBLTB5C1.0M
Documented by the project as a current starting point for compatible hardware setups.
Apple Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter for older TB2 iMac workflows
Documented by the project as a current starting point for compatible hardware setups.
FAQ preview
The setup questions people ask first
The dedicated FAQ page captures the recurring questions: the ETL naming mix-up, native TDM confusion, model support, Thunderbolt 2 adapters, Network Link expectations and Dockstation permissions.
Is TargetBridge a data integration or ETL tool?
No. TargetBridge has nothing to do with MuleSoft, Talend, SAP or Oracle: it is a macOS display-streaming app that turns an old iMac into a 5K external display and input dock for Apple Silicon Macs over Thunderbolt Bridge.
Is TargetBridge native Target Display Mode?
No. TargetBridge is not native Target Display Mode. It is a low-latency Mac-to-Mac display stream built around ScreenCaptureKit, VideoToolbox and Thunderbolt Bridge.
Which Mac can act as the sender?
The current documented sender requirement is an Apple Silicon Mac (M1 or later) running macOS 14 Sonoma or later.
Which Mac can act as the receiver?
The documented receiver path supports Intel or Apple Silicon Macs with a display and Thunderbolt Bridge support. The project ships separate Receiver builds for Intel and Apple Silicon Macs.
Can I use a Thunderbolt 2 iMac?
Sometimes yes, but use the official Apple Thunderbolt 3 to Thunderbolt 2 adapter path. Generic USB-C to Mini DisplayPort adapters are not enough because they do not carry Thunderbolt data.
Author
Who made TargetBridge?
TargetBridge is developed by Marco Caciotti, a senior fullstack developer from Pesaro, Italy, with 22 years of experience. He maintains the project in the open on GitHub, alongside his web development work with Laravel, PHP, Astro and React.
Project links
Go from overview to downloads, docs and support.
The website explains the product story. The repository is where releases, discussions, issues and sponsorship live.