On an LG C or G series OLED, HDMI 1, 2, 3 and 4 are each a full 48Gbps HDMI 2.1 input. That's unusual — most TVs give you one or two fast ports and two slow ones — and it changes the question. You're not hunting for the good port. You're deciding where eARC goes, and turning on the one setting that otherwise caps everything at 4K60.
But "LG OLED" is not one thing, and this is where advice goes wrong. Check which set you have before wiring anything:
- C3 and C4, all sizes — HDMI 1 through 4, each 48Gbps. eARC on HDMI 2.
- B3 — four inputs, but only HDMI 3 and 4 run at 48Gbps; 1 and 2 are limited. eARC is on HDMI 3, which is also one of the two fast ports, so a soundbar and a console will compete for it.
- QNED — not an OLED, and the inputs are mixed. Typically two of the four run at 48Gbps and the other two are limited to 18Gbps, so on a QNED the port you choose absolutely does matter. The manual names which is which.
A console on a QNED's 18Gbps input will never do 4K120, no matter what you change in the menus.
Where to put things
Put the soundbar or receiver on HDMI 2, because that's the only eARC port, and put consoles on the others. There's no performance reason to prefer HDMI 1 over 3 or 4 on a C or G series — they're identical — so the only constraint is not wasting HDMI 2 on something that doesn't need audio return.
The setting that silently caps you at 4K60
Settings > General > Devices > HDMI Settings > HDMI Deep Color, set to On, for the input in use.
Off, the port runs a reduced mode and 4K120 and 4K HDR simply don't appear as options on the console. No error, no message — the capability just isn't advertised, and the console reports the TV can't do it. It's per-input, so switching it on for HDMI 1 does nothing for the Xbox on HDMI 3.
This one setting is behind most "my LG doesn't do 120Hz" complaints, and most LG OLED no-signal reports too.
Then turn on Game Optimizer. It drops input lag to roughly 10 ms and exposes VRR and ALLM. VRR lives under Game Optimizer > VRR, and LG OLEDs are both G-Sync Compatible and FreeSync Premium, so a PC will negotiate G-Sync automatically once Deep Color is on.
The C3 gotcha worth knowing
On the C3, Dolby Vision game mode and VRR are separate toggles. Enabling one doesn't enable the other, and people who turn on Dolby Vision gaming often assume VRR came with it. Check both.
Some early C3 units also had HDMI 2.1 bandwidth negotiation problems with certain AV receivers, fixed by firmware. If you're routing a console through a receiver into a C3 and getting intermittent dropouts at 120Hz, update the TV before you start swapping cables.
Two format limits that surprise people
LG does not support HDR10+. It backs Dolby Vision instead. Content mastered in HDR10+ falls back to plain HDR10 on an LG, which is fine but isn't what the box art promised. This is a real fork in the market — LG and Samsung are on opposite sides of it, and no LG firmware will add HDR10+.
DTS support depends on the model year, and LG has changed its mind twice. It was removed in 2020, restored for the 2023 sets (B3, C3, G3), kept for 2024 (C4, G4), and dropped again for 2025 (C5, G5). So a C3 or C4 decodes DTS, DTS:X and DTS-HD Master Audio on its own speakers and can pass it to a receiver; a C5 cannot, and neither can anything from 2020 to 2022. If you have a DTS disc collection, that single fact should probably decide which model year you buy. Dolby Atmos is decoded internally on all of them.
Per-source setup
PS5 — Settings > Screen and Video, Resolution on Automatic, then enable 120Hz output and VRR. 4K120 is title-dependent, not a blanket mode.
Xbox Series X — after Deep Color is on, the 4K TV Details screen should report 4K120 and VRR. If it doesn't, that screen is telling you Deep Color is still off. Series S renders games at 1440p, so it will never report 4K gaming regardless of the TV.
PC — select G-Sync in the NVIDIA control panel. The OLED identifies as G-Sync Compatible once the port is running full bandwidth.
Cables
A cable that can't carry 48Gbps doesn't fail cleanly. It caps you at 4K60, or gives you intermittent black flicker at 120Hz that looks like a TV fault. Use a Certified Ultra High Speed cable and keep the run short — this is the one place where the certification on the packaging genuinely means something.
See also
FAQ
Which HDMI port is best for gaming on an LG OLED? On a C or G series, any of them — all four are 48Gbps. Keep HDMI 2 free for a soundbar, since it's the only eARC port.
Why won't my LG do 120Hz? HDMI Deep Color is off for that input. General > Devices > HDMI Settings. The console can't see the capability until it's on.
Does the LG OLED support G-Sync? Yes, G-Sync Compatible and FreeSync Premium. Enable VRR under Game Optimizer.
Which port is eARC? HDMI 2 on C and G series, but HDMI 3 on the B3. Never HDMI 1.
Does LG support HDR10+? No. LG uses Dolby Vision, and HDR10+ content plays back as HDR10.
Does my LG decode DTS? Only if it is a 2023 or 2024 model. B3, C3, G3, C4 and G4 do; the 2025 C5 and G5 do not, and nor did 2020-2022 sets.
My QNED won't do 4K120 on HDMI 3. QNED is not OLED and typically has only two HDMI 2.1 ports. Move to one of those.