Quick Answer: A four-way splitter sends one input to four identical outputs, so every display runs at the lowest resolution and refresh rate all four can accept. Bandwidth is needed on each port at the same time, not shared: 1080p60 at 4:4:4 needs 4.45 Gbit/s, 4K60 at 4:4:4 needs 17.82 Gbit/s. A unit rated at 10.2 Gbit/s will fall back to 4K30 the moment one 4K60 panel joins the group. Allow a 5 V power adapter and keep passive output cables under 15 ft (4.6 m) for 18 Gbit/s.
Four sockets on the back do not mean four independent signals. A splitter re-transmits the same stream on every output, and each port has to carry the full data rate of that stream simultaneously. The first thing to check is therefore the highest common capability of the displays, not the port count.
Mirroring, not extending
A splitter duplicates a screen. It cannot give a computer four separate desktops, and it cannot combine inputs. If the requirement is one source to many screens, a splitter is right; if it is many sources to one screen, the device needed is a switch, and the differences are set out in this guide to hdmi splitter switch selection. A 1×4 unit with an unused port behaves exactly like a 1×2 unit; there is no penalty for leaving an output empty.
Bandwidth is consumed per output
TMDS signalling sends the pixel stream on three data pairs plus a clock, and every output port repeats that work. A splitter rated for 10.2 Gbit/s carries 1080p60 or 4K30 cleanly but cannot pass 4K60 at 4:4:4, because that stream is 17.82 Gbit/s. Units rated for 18 Gbit/s handle the full HDMI 2.0 envelope, and 48 Gbit/s units handle HDMI 2.1 features. The practical comparison of the two generations is in hdmi 1.4 vs 2.0.
| Signal | Data rate (Gbit/s) | Passive cable limit | Splitter rating needed |
|---|
| 1080p60 4:4:4 | 4.45 | 50 ft (15 m) | 10.2 Gbit/s |
| 4K30 4:4:4 | 8.91 | 25 ft (7.6 m) | 10.2 Gbit/s |
| 4K60 4:2:0 | 8.91 | 25 ft (7.6 m) | 10.2 Gbit/s |
| 4K60 4:4:4 | 17.82 | 15 ft (4.6 m) | 18 Gbit/s |
| 4K120 4:4:4 | 35.6 | 10 ft (3 m) | 48 Gbit/s |
EDID and HDCP decide whether it works
EDID: copy one port or manage the set
EDID tells the source what the sink supports. Cheap splitters copy the EDID of output one only, so a 4K panel on port one and a 1080p projector on port two leaves the projector showing a blank screen. A unit with EDID management can present a fixed 1080p profile to the source, which then feeds all four ports at 1080p. Where displays differ, force the lowest common format at the splitter rather than at the source.
HDCP: one failed handshake blocks all ports
Protected content needs HDCP 2.2 on the whole chain for 4K, and a single legacy display in the group can pull the entire output down to 1080p or to a black screen with an authentication error. HDCP 1.4 devices in the group also add 1 to 2 seconds of handshake delay each time the source renegotiates.
Connectors, couplers and power
Every extra mating pair costs signal. A hdmi coupler used to join two 15 ft leads makes a 30 ft chain with three connectors, and 18 Gbit/s links often fail at that point even though each half tested clean. Power the splitter from its own 5 V supply: bus power over HDMI is limited to 50 mA at 5 V, which is not enough for the retiming circuitry and explains outputs that drop when a second display is connected.
Practical scenarios
- Situation: A sports bar feeds four 1080p60 televisions from one tuner. A 10.2 Gbit/s splitter with a 5 V supply and 25 ft (7.6 m) passive leads on each output is sufficient and costs less than an 18 Gbit/s unit.
- Situation: Two 4K60 monitors sit beside a 1080p confidence monitor. Force 1080p60 at the splitter with EDID management, because mixed EDID copying produces flicker every time the confidence monitor wakes.
- Situation: A conference room needs 4K60 on a 40 ft (12 m) run. Use an 18 Gbit/s splitter plus a fibre or active optical lead for that output, and passive 6 ft leads for the local displays.
- Situation: Output four shows a picture for two seconds then drops. The display is HDCP 1.4 only, so replace it or fit an HDCP converter on that single output.
FAQ
Can a splitter feed four screens at different resolutions?
Not with different resolutions at the same time. All outputs carry the same stream, so every display must accept the format the source is sending. Displays that cannot accept it show a blank screen or drop to a lower mode on their own.
Why does one output fail while the others work?
The usual causes are a longer cable on that port, a display with older HDCP, or a connector that has lost a TMDS pair. Swap the suspect cable to a working port first; if the fault follows the cable, the cable is the problem.
Does a splitter reduce picture quality?
No, because the digital stream is retransmitted, not divided. What changes is the format: if the splitter cannot carry the bandwidth, the source drops to a lower resolution or chroma sampling, and that is a visible loss rather than a gradual one.
