HDX (High Definition Experience)
Citrix’s proprietary display protocol. On the market for more than 20 years, designed for poor networks, multimedia and peripheral redirection.
What is HDX?
HDX stands for High Definition Experience and is Citrix’s display protocol portfolio. It is not a single protocol but a collection of technologies that together optimise the transfer of screen, audio, input devices and peripherals between session host and endpoint.
Its historical origin is the ICA-Protokoll (Independent Computing Architecture) of the early 1990s — one of the first commercial remote display protocols of any kind. What is called HDX today is its modern evolution.
What sets HDX apart from other protocols
Microsoft’s RDP and Omnissa’s Blast Extreme are good protocols for standard scenarios. HDX shows its strengths in the difficult cases: poor networks, high latency, unusual peripherals, graphically demanding applications.
Die wichtigsten HDX-Technologien
| Component | Purpose | Advantage |
|---|---|---|
| Adaptive Transport (EDT) | Switches dynamically between TCP and UDP | Up to twice the session performance on poor networks |
| HDX 3D Pro | GPU acceleration for CAD and 3D | NVIDIA GRID, AMD, Intel Support — weitgehend verlustfrei |
| HDX Media Stream | Multimedia redirection (YouTube, Teams) | Video is rendered locally, not on the server |
| HDX RealTime Optimization | Optimisation for Teams and Skype for Business | Audio and video run directly from the device, not through the server |
| HDX USB Redirection | Specialist devices to the session host | Point-of-sale scanners, medical devices, signature pads and the like |
| HDX Universal Print | Druckertreiber-freies Drucken | Any local printer works without server configuration |
| HDX Adaptive Audio | Adjusts audio quality dynamically | Bitrate adapts to network conditions |
EDT: the heart of modern HDX
Enlightened Data Transport (EDT) is Citrix’s UDP-based transport protocol, which has supported HDX since around 2016. The background: on poor networks TCP becomes problematic, because it insists on retransmissions that produce visible lag in a remote desktop scenario.
How EDT solves the problem
- UDP-basiert — no TCP header overhead, no automatic retransmissions
- Eigenes Flow-Control — Citrix implements intelligent retransmission at a higher level
- Dynamisches Fallback — where UDP is blocked (firewalls), EDT falls back to TCP automatically
- Forward Error Correction (FEC) — redundant data is sent proactively, so short bursts of packet loss cause no noticeable lag
Measurably better at high latency: Citrix’s own benchmarks show that at 200 ms latency and 2% packet loss, EDT keeps a session fluid while TCP-based protocols become unusable. For offshore team scenarios (India, the Philippines, remote parts of Africa) this is often decisive.
HDX compared with other protocols
| Aspekt | HDX (Citrix) | RDP (Microsoft) | Blast Extreme (Omnissa) |
|---|---|---|---|
| LAN performance | Very good | Very good | Very good |
| High latency (200 ms and above) | Best | Moderate | Good |
| Multimedia/Teams | Very good (with redirection) | Very good (Teams optimisation) | Very good |
| USB peripherals | Best | Good | Good |
| 3D/CAD | HDX 3D Pro | RemoteFX (deprecated) | Blast 3D |
| Available in | The Citrix stack only | Windows natively, AVD, RDS | The Omnissa stack only |
Is HDX still relevant in 2026?
The short answer: yes, but less universally than five years ago.
Microsoft has improved RDP enormously in recent years (Teams optimisation, RDP Shortpath over UDP, App Attach). For the 80% standard office scenario on a LAN or a good internet connection, the protocol hardly matters today — all three (HDX, RDP, Blast) deliver good results.
The remaining 20% — the high-end use cases — remain Citrix territory:
- Offshore-Teams with 150 ms of latency and more, and fluctuating packet loss
- Retail-Szenarien with receipt printers, barcode scanners and customer displays
- Medizin with high-resolution image archives (radiology) and specialist input devices
- Engineering with CAD software that has to use the GPU
- Video-Conferencing in contact centres with strict latency commitments
HDX in protocol comparison
DaaS Maps compares HDX in detail with Blast Extreme, RDP and PCoIP — with real latency scenarios and a feature matrix. For discussion of protocol choice, you will find me on LinkedIn.