What is the difference between part fibre, cable and full fibre?

Where the fibre actually stops on each kind of connection, why that decides your speed, and the one thing full fibre changes about your phone.

Difficulty: beginner
Time: 15 min
Read: 4 min

Short answer

The only real difference is how far the fibre reaches before copper takes over. Part fibre stops at the street cabinet and runs copper to your house, so distance from the cabinet caps your speed. Full fibre runs the whole way in and ends in a small box on your wall, so distance stops mattering — but it carries no analogue phone line.

For a decade almost everything was sold as 'fibre broadband' whether or not fibre reached the house. The distinction matters because it is the single thing that determines whether the speed you are offered is a promise or an average.

Where the fibre stops on each kind of broadband

Step by step

Find out what your line actually is.Your provider's account pages will name the product. Ofcom and the network operators also publish availability checkers — always check by full address, because availability varies house to house on the same street.
Recognise part fibre, sold for years as 'fibre'.Technically fibre to the cabinet. Fibre runs to the green box in the street; the last stretch is the old copper telephone line. Speeds are typically in the tens of megabits and fall with distance from that cabinet.
Recognise cable.Fibre to a local point, coaxial cable into the house. Faster than copper, but the local segment is shared, so evening speeds can dip when the neighbourhood is busy.
Recognise full fibre.Fibre to the premises: a fibre strand the whole way in, ending in a small wall box called an optical network terminal. No copper anywhere, so distance to the exchange no longer sets a ceiling.
Look at the upload speed, not just the download.This is where the gap is starkest. Part fibre commonly offers around a tenth of the download for upload; full fibre often offers the same in both directions, which is what makes video calls, cloud backups and sending large files feel different.
Expect an engineer and a new box for a first full fibre install.A cable is run to the house, a wall box is fitted inside, and the router plugs into it. Allow a few hours and decide in advance where you want that box, because the router has to sit near it.
Plan for the phone line before you switch.Full fibre carries no traditional analogue line. The handset plugs into the router instead, and it stops working in a power cut. If anyone in the house depends on a phone, a care alarm or a monitored alarm, tell the provider before the order goes in.
Ignore the headline number and read the guaranteed minimum.UK providers must give a minimum guaranteed speed at the point of sale. If your line persistently falls below it and they cannot fix it, you can usually leave without a penalty.

Tips

Two neighbours can be offered very different part-fibre speeds purely because of cable length back to the cabinet. Always check by address.
Full fibre's biggest practical gain for most households is not the download figure — it is the upload speed and the stability in wet weather.
A new full fibre order sometimes means a new phone number arrangement. Confirm what happens to your existing number in writing before you agree.

Common mistakes

Assuming 'fibre broadband' means fibre to the house — For most of the last decade it did not. The last stretch was copper, which is why the speed varied so much between neighbours on the same package.
Ordering full fibre without checking what happens to the landline — The analogue line goes away with it. Care alarms, monitored alarms and some medical pendants need to be reconfigured or replaced first, not afterwards.

If it doesn't work

Speed is far below the advertised figure

Cause: On part fibre, distance from the cabinet; on any line, wifi rather than the line itself — Fix: Test with a device plugged into the router by ethernet cable. If the cable result is fine, the problem is wifi, not broadband.

Speeds drop every evening

Cause: Local congestion, most common on cable and on oversubscribed part-fibre cabinets — Fix: Record speeds at several times of day for a week and report the pattern; a consistent evening collapse is a fault worth raising.

Full fibre is 'available' but the order keeps failing

Cause: The network is built past the street but not yet connected to the property — Fix: Ask the network operator, not the retailer, whether the property has a live connection point. They are different companies.

Landline dead after a broadband change

Cause: The line was migrated to a router-based service and the handset is still in the wall socket — Fix: Plug the handset into the phone socket on the back of the router. Ask the provider for a battery backup unit if anyone in the house needs a phone in a power cut.

Questions people ask

Is full fibre worth paying more for?

For a household with several people streaming, working from home or backing up to the cloud, usually yes — mostly for the upload speed and the stability. For one or two people browsing and watching television, a good part-fibre line is often enough.

Will full fibre fix my wifi?

No. It replaces the line into the house, not the signal inside it. If the problem is a far bedroom or a thick wall, faster broadband arrives at the router and stops there.

Can I keep my phone number?

Usually yes, both when switching provider and when moving to full fibre, but it must be requested as part of the order rather than afterwards.