Free tool · hardware bottleneck finder
Why isn’t your 4K telly showing proper 4K?
Fast broadband and a 4K TV, but the picture still looks soft or juddery on the sport? Software can’t fix that — it’s almost always a physical bottleneck: an old HDMI cable, the wrong port, or a setting switched off. Answer four quick questions and we’ll pinpoint the weak link and how to fix it.
HDMI versions and 4K: what each one can actually carry
The HDMI standard printed on your cable (and built into your TV’s port) sets a hard ceiling on the picture — no app or setting can push past it.
| HDMI version | Also labelled | Max 4K | Bandwidth |
|---|---|---|---|
| HDMI 1.4 | High Speed | 4K @ 30Hz | 10.2 Gbps |
| HDMI 2.0 | Premium High Speed | 4K @ 60Hz | 18 Gbps |
| HDMI 2.1 | Ultra High Speed | 4K @ 120Hz · 8K | 48 Gbps |
How to unlock full 4K UHD on your TV
Three checks fix almost every “my 4K TV looks soft” case: 1) use a cable marked Premium High Speed (4K@60) or Ultra High Speed (4K@120); 2) plug into your TV’s fastest HDMI port — on many sets only one or two are full-speed, often labelled 4K/UHD/2.1; and 3) turn on the enhanced-HDMI setting for that port — Samsung Input Signal Plus (older: HDMI UHD Color), LG HDMI Deep Colour, Sony HDMI enhanced format. With those sorted, IPTV UK’s up-to-4K streams show at their full quality. New to setup? The setup wizard builds your device’s steps, and the troubleshooter handles anything else.
HDMI & 4K FAQs
Why isn't my 4K TV showing 4K?
Almost always one of three physical things is capping it: an old HDMI 1.4 cable that can only carry 4K at 30Hz, a slower HDMI port on the TV, or the TV’s enhanced-HDMI setting being switched off for that port. Fix the weak link and the same stream jumps to full 4K at 60Hz.
What HDMI cable do I need for 4K?
For 4K at 60Hz you need at least an HDMI 2.0 cable, usually labelled Premium High Speed (18 Gbps). For 4K at 120Hz you need HDMI 2.1, labelled Ultra High Speed (48 Gbps). An old HDMI 1.4 cable only manages 4K at 30Hz, which makes sport and fast motion look juddery.
How do I turn on 4K on a Samsung or LG TV?
On Samsung, enable Input Signal Plus (older sets call it HDMI UHD Color) for the HDMI port you use. On LG, enable HDMI Deep Colour for that port. On Sony it’s HDMI enhanced format. Without this setting many 4K TVs quietly fall back to 4K at 30Hz or reduced colour.
Does it matter which HDMI port I use on my TV?
Yes. On many TVs only one or two of the HDMI ports run at full speed for 4K at 60Hz or 120Hz, and they’re often labelled 4K, UHD or 2.1. Plugging into a slower port limits the picture, so if 4K isn’t showing, try a different port first.