What the lights on the white Openreach box mean

Most broadband advice assumes there is one box. On a full fibre line there are usually two: your hub, and a smaller white box fixed to the wall with a thin cable running into it. That white box is where the fibre actually arrives, it has its own mains plug, and it can fail entirely on its own — which is why a perfectly healthy-looking hub can sit next to a dead connection.

This page covers the white box and the Digital Voice adapter. If it is your hub you are standing in front of, we have a page for every model and every colour: BT hub lights, EE hub lights, Sky router lights and Virgin Media hub lights.

Which box are you looking at?

Three different things get called “the router”, and they mean different things when they misbehave.

• The hub — the big one, with the Wi‑Fi in it, usually with a single large status light on the front. This is the one your provider sent you.
• The Openreach modem, or ONT — a slim white box screwed to a wall or skirting board, usually near where the cable enters the house. It has several small labelled lights: POWER, PON, LOS and a row of numbered PORT lights. A thin white fibre cable goes into it, and an ordinary Ethernet cable comes out of it into your hub. It has its own plug.
• The Digital Voice adapter — a small plug-in unit with one light and a telephone socket on top, which your home phone plugs into.

Only full fibre (FTTP) lines have the Openreach modem. If your broadband arrives over the phone line, there is no white box and your hub is the whole story.

The Openreach modem, light by light

BT documents these as combinations, not one light at a time, and that matters: PON and LOS only make sense read together. The healthy state is PON solid green with LOS off.

Light	What you see	What it means	What to do
POWER	Green	The modem is on	Check PON and LOS next
POWER	Off	The modem is off	Check the mains plug is in and switched on
PON and LOS	PON solid green	The fibre link to the exchange is working and recognises your modem	The fibre side is fine. Check the cable between the modem and your hub at both ends, and try a spare
PON and LOS	PON flashing, LOS off	The modem is checking in with the exchange	Wait until it turns solid green
PON and LOS	PON off, or PON and LOS both flashing	The fibre link is not connected, or there is a problem between your property and the exchange	Check the thin white fibre cable is inserted and undamaged. Power the modem off, back on, and wait five minutes
PORT 1–4	Any one lit	The Ethernet connection to your hub is normal (port 1 is the one the engineer uses)	If you are still offline, the problem is past the modem — check your hub
PORT 1–4	Any one blinking	Data is moving through that port	Normal
PORT 1–4	All off	The Ethernet cable to the hub is not plugged in, or is broken	Check the cable at both ends and try a spare
TEL 1–2	Lit	The fibre home phone line is live on the modem	Nothing
TEL 1–2	Blinking, or all off	The fibre home phone line is not activated	If it should be active, check the modem is powered and raise it with your provider

What the LOS light is actually telling you

LOS stands for loss of signal, and it is a light you want to see doing nothing at all. Openreach’s own check is refreshingly blunt: if the PON light is solid green and the LOS light is off, it is working properly.

What no official source does is separate a flashing red LOS from a steady red LOS. Third-party sites state this confidently — flashing means a broken fibre, steady means lost signal, or some variation of it — but BT documents the LOS light only alongside PON, and Openreach’s page does not describe LOS colours at all. There is no first-party basis for the distinction, so we are not going to repeat it. Photograph the lights instead, and describe exactly what you see, in those words, when you report the fault.

Do not ring Openreach

This is the single most common wasted afternoon in fibre faults. Openreach owns the fibre and the white box, but it does not take fault reports from consumers. Openreach’s own advice is to contact the company you buy your broadband from, because there may be a problem with their network.

So report it to whoever you pay — BT, EE, Sky, TalkTalk, Plusnet, Vodafone or an altnet — even though the box on your wall has someone else’s name on it. They raise it with Openreach on your behalf.

What to do when the lights are wrong

1. Check the modem has power. If the POWER light is off, the modem is off. Check its mains plug and switch — it has its own, separate from the hub, so it can be dead while everything else looks fine.
2. Check the thin white fibre cable. Make sure it is pushed fully in and is not kinked, crushed or damaged. Do not pull it out to look at the end; fibre breaks easily and you cannot repair it yourself.
3. Power the modem off, then on, and wait five minutes. Leave it alone for the full five minutes while it tries to reconnect. Restarting it again during that window is the most common way people extend their own outage — the same trap covered in how to restart your router properly.
4. Read PON and LOS together. Solid green PON with LOS off means the fibre is healthy and the fault is further in. PON off, or both flashing, means the link to the exchange is not working.
5. Check the Ethernet cable to the hub. If the fibre side is healthy but you are still offline, check that cable at both ends and try a spare. All the numbered port lights off means the modem cannot see your hub at all.
6. Report it to the company you pay, not to Openreach — and do it the same day, for the reason in the next section.

Before you report it, it is worth thirty seconds on is my broadband down? to see whether it is an area fault. If it is, there is nothing to fix at home. And if the connection is completely dead, our step-by-step plan for what to do in a broadband outage covers the whole sequence, including how to get online while you wait.

The clock starts when you report it

Under Ofcom’s automatic compensation scheme, a total loss of service that is still not fixed two full working days after you report it earns £10.34 for each calendar day it stays broken, at the rates in force from 1 April 2026. A missed engineer appointment, or one cancelled with less than 24 hours’ notice, is £32.31. A delayed start to a new service is £6.46 per day. It should be credited to your bill within 30 calendar days without you having to claim.

Two exclusions matter, and they are the reason this page is worth reading before you pick up the phone. Nothing is due where the fault started inside your own premises, and nothing is due where you delayed the repair by turning down offered appointments. Working out whether the problem is the modem, the fibre or your own Ethernet cable is exactly the difference between a fault that pays and one that does not.

Ten providers take part: BT, EE, Hyperoptic, Plusnet, Sky (including NOW), TalkTalk, Utility Warehouse, Virgin Media, Vodafone and Zen. See automatic compensation explained, or work out what you are owed.

The Digital Voice adapter

If your home phone now plugs into a small adapter rather than into the wall socket, your phone service runs over your broadband. The adapter has one light, and it is always green — there is no colour code to learn, only a rhythm.

What the light does	What it means
Flashes 0.5 seconds on, 2 seconds off	You have just plugged it in — or there is a problem with your broadband connection
Flashes quickly, 0.5 seconds on and off	It is registering with your hub
Steady green	Registered and ready
Flashes slowly, 1 second on and off	A call is in progress

That first row is not a mistake on our part. BT’s own user guide gives the same flash pattern two different meanings — “on initial plug in”, and “once registered, if there’s a connection problem with your broadband”. So a slowly flashing adapter tells you very little on its own. Look at your hub light and the white box as well: if those show a fault, the adapter is reporting the same fault rather than a separate one.

Two things BT states plainly in the same guide, both worth knowing before you need them:

• You cannot call 999 during a power cut or a broadband problem from a phone plugged into your hub or a Digital Voice adapter. Make sure there is another way to call for help.
• A home phone more than about ten years old may simply not work with the adapter.

If anyone in the home uses a telecare pendant, a fall detector or a medical alarm, that first point is not an inconvenience. Read will my alarm still work after the landline switch?, and the landline switch-off explained for the wider picture.

It is the hub, not the white box

If the Openreach modem shows PON solid green and LOS off, the fibre is doing its job and your answer is on the hub. These pages list every state each manufacturer documents, per model, with the source and the date it was checked:

• BT hub lights — Smart Hub 2, Smart Hub 3, Smart Hub and Ultrafast Smart Hub, Home Hub 4 and 5
• EE hub lights — Smart Hub 2023 and 2021, Smart Hub 6 Plus, 7 Plus, 7 Pro, Smart Router
• Sky router lights and Virgin Media hub lights
• What router lights mean in general, if you are not sure who made your hub

Two traps are worth naming here, because they are the ones that send people to the wrong answer.

On a BT Smart Hub 2, purple means two opposite things. Steady purple means the hub is connected to the EE mobile network using Hybrid Connect — your broadband is down, but you still have internet, and the underlying fault still needs reporting. Flashing purple means the opposite kind of problem: the hub is working but the broadband cable is not connected. One says “you are fine for now”; the other says “nothing is coming in”. If yours is steady purple, report the fault anyway, because otherwise the outage runs on unreported and no compensation clock ever starts.

EE has used three different colour schemes across hub generations. The 2023 Smart Hub uses blue, orange and purple. The 2021 Smart Hub has no purple at all and uses aqua and yellow instead. The 7 Pro and 7 Plus use aqua again but move mobile backup to white. A chart from the wrong generation will confidently give you the wrong answer, so check your model before you read any colour table. The model name is normally on a label underneath or on the back.

The lights are fine but it is still slow

If the modem is healthy and the hub says it is connected, then the connection is up, and what you have is a speed, Wi‑Fi or quality problem rather than an outage. Run a speed test wired if you can, check the figure here, then fix slow internet or fix slow Wi‑Fi.

If the speed test comes back with a perfectly good number and the connection still feels broken, that is its own problem with its own causes — speed test fine but the internet feels broken covers what a speed test does not measure.

One confusion worth clearing up while you are here: the Wi‑Fi light only tells you your home network is broadcasting. It says nothing about whether your provider is reachable. See wired vs Wi‑Fi speed.

If you have to call

Have these ready. It genuinely shortens the call, and it strengthens a complaint later if the repair drags on.

• The colour and pattern of each light — steady or flashing, and which light. Photograph both boxes.
• Whether the white Openreach box has power at all.
• When it started, to the hour.
• What you have already tried, especially the five-minute power cycle.
• Whether neighbours on the same provider are affected.

BT customers can reach broadband technical support on 0330 1234 150, or 150 from a BT mobile, Monday to Friday 8am–9pm and weekends and bank holidays 8am–8pm. BT says the 0330 number is free from the BT network; other networks may charge.

Ask for a fault reference number and write it down. If the repair drags on, how to complain about your broadband and the complaint letter generator take it from there.

→ Use the is my broadband down? checker