Broadband jargon explained: an A to Z

These words describe how the internet physically reaches your home, which shapes the speeds you can be offered. Openreach's consumer product pages quote these figures (checked October 2026):

That full fibre figure isn't a ceiling. ISPreview reported in August 2026 that Openreach's fastest consumer full fibre packages reach 1.8Gbps download, and its XGS-PON pilot up to 8.5Gbps; EE has sold Full Fibre 8 Gigabit on the pilot since 31 July 2026, around Guildford and Woking. Other full fibre networks sell multi-gigabit tiers too. See XGS-PON explained.

ADSL and ADSL2+. Asymmetric Digital Subscriber Line: broadband over the copper phone line. "Asymmetric" means download is much faster than upload. thinkbroadband notes that ADSL2+ raised the maximum download connection speed from 8Mbps to 24Mbps. Speeds fall the further you are from the exchange.

Cable, DOCSIS and HFC. Virgin Media's original network runs fibre to a local cabinet and coaxial cable for the last stretch, a design called hybrid fibre-coax (HFC). DOCSIS is the standard that carries data over it. thinkbroadband explains that the coax doesn't lose speed with distance the way phone copper does. Virgin Media's Hub 5 connects using DOCSIS 3.1. See Virgin Media broadband deals and our guide to how Virgin Media's network differs from Openreach.

"Fibre" labelling. Since 16 September 2024, Ofcom's guidance (as reported by ISPreview) says providers should describe the technology on their websites and in contract information with clear terms such as full fibre, part-fibre, cable or copper, not "fibre" on its own. "Full fibre" is for fibre to the home (fibre to the building is allowed for now). Adverts are covered by the Advertising Standards Authority (ASA) instead.

Fixed wireless (4G or 5G home broadband). A hub picks up a mobile signal and turns it into Wi-Fi, with no line needed. Three, for example, says speeds aren't guaranteed and depend on where the hub sits and how many people nearby are using the network. Compare Three broadband deals.

FTTC (Fibre to the Cabinet). Fibre runs to the roadside cabinet and the existing copper phone line covers the last stretch. Openreach says it is also called superfast or VDSL, reaches 96% of the country, and can slow noticeably beyond roughly 300 to 400 metres from the cabinet. Our guide to slow broadband on a long line explains why.

FTTP, FTTH and FTTB. Fibre to the Premises, also called Fibre to the Home or full fibre, runs fibre into your home. Fibre to the Building takes fibre to the building itself, such as a block of flats. Browse fibre broadband deals, or read what full fibre broadband is.

G.fast and SOGfast. G.fast is the ITU-T standard "Fast access to subscriber terminals". Like FTTC, fibre runs to the street cabinet and the existing copper line covers the last link. SOGfast (Single Order G.fast) is Openreach's version without a separate phone line. Our guide what is G.fast covers what is happening to it.

SOGEA. Single Order Generic Ethernet Access: Openreach's data-only version of FTTC broadband. FTTC was originally sold alongside a phone line rental product (see WLR below); SOGEA drops it. On an order, it means part fibre broadband with any home phone running digitally over it.

VDSL2. Very High Bit Rate Digital Subscriber Line 2, the technology behind FTTC, defined in the ITU-T standard G.993.2. thinkbroadband's explainer of UK FTTC says it uses frequencies up to 17MHz.

Altnet. Short for alternative network: a company that has built its own full fibre network rather than reselling Openreach's. ISPreview's consolidation tracker counted around 80 of them in late 2025 and expects mergers to shrink that number. Each covers particular areas. Some sell to households directly; others run open access (wholesale) networks that several providers sell over, such as CityFibre or Freedom Fibre, which Pop Telecom joined in November 2025 (ISPreview). On an open access network your contract, and any service question, is with the provider you signed up with, not the network. See what an altnet is and our guide to broadband providers.

GPON. Gigabit-capable passive optical network (ITU-T G.984). Openreach's full fibre is still largely GPON (ISPreview, August 2026). The ITU's G.984.1 specification describes nominal line rates of 2.4Gbit/s down and 1.2 or 2.4Gbit/s up. thinkbroadband explains that the fibre is split closer to each property, so capacity is shared at some point.

ONT (Optical Network Terminal). On Openreach full fibre, the small box inside your home where the fibre ends. Openreach says its job is to turn the incoming fibre signal into something your router can work with, and that "it's not a router, and it's not a traditional modem". It belongs to Openreach, not you or your provider, so you leave it in place when you switch and the new provider uses the same ONT. Our guide to the ONT and your router covers set-up.

ONT lights: PON, LAN and LOS. Openreach says steady PON and LAN lights mean the ONT is connected, while a red LOS light, a flashing PON light or no lights at all can mean a problem; if it persists, contact your broadband provider.

Openreach. A wholly owned but legally separate company within BT Group that looks after the copper and fibre lines. Its customers are broadband providers, over 650 of them, and its engineers work on your provider's behalf, so you arrange installs and report faults through the provider. See what Openreach is, and if you are unsure whose network you use, which network your broadband is on.

PON (passive optical network). The design used for full fibre, in which a fibre is split to serve several homes, so capacity is shared. GPON and XGS-PON are both types of PON.

XGS-PON. The ITU-T standard G.9807.1, titled "10-Gigabit-capable symmetric passive optical network". Symmetric means the same capacity in both directions. Virgin Media's Hub 5x connects to its full fibre using XGS-PON. ISPreview reports that Openreach's XGS-PON pilot has been open to providers since 23 March 2026, covering Guildford and neighbouring Woking, and (August 2026) that Openreach plans to reach more than a million premises by the end of August 2027; existing Openreach full fibre customers typically need a new 10Gbps-capable ONT fitted to use it. Our guide to XGS-PON explains what it changes.

Download and upload (downstream and upstream). Download is data coming to you from the internet; upload is data you send, such as video calls and backups. See download vs upload speed.

Mbps, Gbps and MB/s. Broadband is measured in megabits per second (Mbps); there are 1,000 megabits in a gigabit (Gbps). A capital B means bytes, and there are 8 bits in a byte, so a download shown in MB/s (megabytes per second) is about one-eighth of the Mbps figure. Our guide to broadband speed units has worked examples.

Superfast, ultrafast and gigabit-capable. In GOV.UK's Project Gigabit guidance, anything over 30Mbps counts as superfast and over 100Mbps as ultrafast, while gigabit-capable means a wired connection that can download at least 1Gbps. Ofcom used 300Mbps and above for ultrafast from 2015, so the same word can mean different things. Superfast, ultrafast and gigabit explained sets out both.

DLM (Dynamic Line Management). On copper and part fibre lines, an automatic system that can adjust a line's speed to keep it stable. thinkbroadband explains that restarting your router often can make the line look unstable, so DLM may slow it down to steady it.

G.INP and interleaving. Terms from part fibre line performance. thinkbroadband's glossary (around 2017 to 2018) calls G.INP an improved error-correction system and says interleaving can give FTTC lines more latency (delay) than ADSL2+, while G.INP loses less speed.

Hub, modem and router. A modem translates the signal on the line into a data connection; a router shares that connection between your devices and creates your Wi-Fi. A provider's "hub" usually combines both: Virgin Media says "a Hub is a modem and a router in one". On Openreach full fibre the router plugs into the ONT instead. Our guide to broadband vs Wi-Fi walks through the chain.

Mesh Wi-Fi. A set of access points that behave as a single network, with each phone or laptop guided to whichever point serves it best. EasyMesh is the Wi-Fi Alliance's standard for this.

SSID (service set identifier). The name of your Wi-Fi network, the one you pick on your phone. Which? notes the name and password usually come on a card with the router or a sticker on the back.

Sync speed. The connection speed your router shows on a copper or part fibre line. thinkbroadband says that because of protocol overheads (extra data added to every packet), a speed test normally shows about 86% to 96% of it. Our guide to reading your router's line statistics covers the other figures, and you can check real throughput with our broadband speed test.

Vectoring. A technique that cancels cross-talk (interference) between part fibre lines in the same cable bundle. thinkbroadband's glossary, written around 2017 to 2018, noted that it wasn't used on every Openreach cabinet at the time.

Wi-Fi 6, 6E and 7; 2.4GHz, 5GHz and 6GHz. Generation names set by the Wi-Fi Alliance, which dates Wi-Fi 5 to 2014, Wi-Fi 6 to 2018 and Wi-Fi 7 to 2024. 2.4GHz suits basic needs such as browsing and smart gadgets, 5GHz suits demanding uses, and the newer 6GHz band needs a Wi-Fi 6E or Wi-Fi 7 device. See Wi-Fi 6, 6E and 7 explained.

CDN (content delivery network). Servers in many places holding copies of the same content, so you are served from one close to you.

CGNAT (carrier-grade NAT). A way of sharing one public IPv4 address between many customers. It means you don't get your own public IP address, and thinkbroadband says it can break some applications such as online gaming or internet calling. ISPreview's 2024 survey found most providers do a poor job of saying whether they use it, so if you play online games or make internet calls, ask a provider about it before you sign. See CGNAT, static IP and IPv6.

DNS (Domain Name System). The internet's naming system, which looks up the numeric address behind a name such as a website address. See what DNS is.

IP address, IPv4 and IPv6; dynamic and static IP. An IP address identifies your connection on the internet, much like a phone number. IPv4 has about 4.3 billion addresses; IPv6 offers vastly more. A dynamic IP can change when your connection resets; a static IP stays the same and can cost extra with some providers.

IXP (Internet Exchange Point). A physical location where networks connect and swap traffic directly, known as peering.

Latency, ping, jitter and packet loss. Latency is the time data takes to travel across a network; a ping test times a round trip to a server and back, in milliseconds. Jitter is packets arriving at uneven rates, which can cause missing words on calls, and packet loss is data that never arrives. See latency, ping and jitter.

Traffic management. Providers may manage traffic, but the rules say it must be transparent, non-discriminatory and proportionate, not based on commercial considerations, and must not monitor specific content.

ADR (alternative dispute resolution). The free, independent route for a complaint your provider hasn't put right. There are two Ofcom-approved schemes, CISAS and the Communications Ombudsman, and a provider serving households has to be a member of one of them. For complaints first raised on or after 8 April 2026 you can go to ADR six weeks after first complaining (it was eight weeks before), or straight away if the provider sends a deadlock letter. See how to complain.

Automatic compensation. Ofcom's scheme is voluntary, but most large providers have signed up, including BT, EE, Plusnet, Sky, Virgin Media, Vodafone and Zen (ISPreview, April 2026). If a total loss of service isn't fixed two full working days after you report it, a signed-up provider pays £10.34 for each calendar day it stays unfixed (rate from 1 April 2026), with no claim needed. See automatic compensation.

Contract summary. A short document, normally no more than one A4 page (three for bundles), that you must be given before you sign, including the speeds section described above. Our guide to your contract summary explains each part.

Cooling-off period. A new order taken online or by phone can be cancelled within 14 calendar days. If the service has started you may pay for what you used.

Early termination charge (ETC) and minimum term. The minimum term is the period you commit to; BT says its are usually 12, 18 or 24 months. Leave before it ends and you may pay an ETC, which Virgin Media calls an early disconnection fee. After the term, Virgin Media's contract, for example, rolls monthly and can be cancelled with 30 days' notice and no fee.

End-of-contract notification. Since February 2020, providers must contact you, usually 10 to 40 days before your minimum term ends, with the end date, what you will pay afterwards and their best deals.

Mid-contract price rise. Since 17 January 2025, new contracts cannot use inflation-linked or percentage rises; any rise must be set out in pounds and pence when you sign. See mid-contract price rises.

OTS (One Touch Switch). The switching process Ofcom introduced on 12 September 2024. The only company you contact is the one you are joining, and it arranges the handover. Your current provider still has to send you the switching information, including any early termination charges you would owe, so you know what leaving will cost. It applies to home phone and fixed broadband, including moves between separate networks, and any gap in service should be no longer than one working day where technically possible. Read our guide to switching broadband.

Social tariff. Cheaper broadband for people on certain benefits. Ofcom's social tariffs page (updated 17 August 2026) says current prices range from £10 to £24 a month and most offer over 30Mbit/s, but check the provider's own page for the current price and who qualifies. See social tariffs explained and cheap broadband deals.

USO (Universal Service Obligation). A right to request a better connection where a home can't get at least 10Mbit/s download and 1Mbit/s upload. Requests go to BT, or to KCOM in the Hull area, and eligibility rules apply. See the broadband USO.

Digital Voice, VoIP and All-IP. Names GOV.UK uses for landline calls carried digitally over your internet connection, replacing the old analogue network. Digital Voice is also the name BT gives its own broadband-based home phone service, so other providers may use a different label for the same idea. See the digital landline switchover.

EVAc (Emergency Voice and Access Continuity). Openreach says anyone not moved to a digital service by 31 January 2027 may be put on EVAc: a temporary, voice-only service that keeps basic calls working for a limited time and may not support every calling feature.

PSTN (Public Switched Telephone Network). The analogue phone network, which Openreach says is being retired in January 2027.

Stop sell. No new sales of a product, while existing customers keep it until it is withdrawn. Under Openreach's FTTP Priority Exchange stop sell, once full fibre (ultrafast) coverage in an exchange area reaches 75% and 12 months' notice has passed, homes there that can get full fibre can only order full fibre; homes without it can still order copper-based broadband. See Openreach stop sell and Openreach exchange closures.

Wayleave. Permission from a landowner for a network to put equipment on their land, under the Electronic Communications Code. See wayleaves explained.

WLR (Wholesale Line Rental). The old copper phone line rental product. Openreach stopped new sales on 5 September 2023 and withdraws it on 31 January 2027.

1. Work out the technology. Look past the headline label to the description: full fibre (FTTP), part fibre (FTTC or SOGEA), cable or 4G/5G.
2. Read the speed figures, not the band. "Ultrafast" is vague; the minimum guaranteed and normally available speeds in the contract summary are not.
3. Check the price rise wording. On a new contract it should be a pounds-and-pence amount.
4. Note the minimum term and how the ETC is worked out, and what happens after the term ends.
5. Ask about the phone. If you need a landline, it will be digital. If you rely on a phone-line device such as a personal alarm, tell the provider.
6. Ask about kit. Which router you get, whether it must be returned, and on full fibre whether an ONT is already fitted.

When you're ready, compare deals at your postcode to see the speeds and deals available at your address. We compare deals but don't switch you ourselves; the provider you choose handles the order.