What Is an ISP? Internet Service Providers Explained (2026)

**An ISP, or Internet Service Provider, is a company that supplies your home with internet access. In the UK, ISPs either own their own network infrastructure, like Virgin Media, or lease capacity from network operators such as Openreach. Major UK ISPs include BT, Sky, Virgin Media, Vodafone, and TalkTalk. ISPs manage your connection, set pricing, handle customer service, and route your traffic to the wider internet.**

What an ISP Does

An Internet Service Provider connects your home to the global internet. When you sign up for broadband, your ISP provisions a connection on its network, assigns you an IP address, and routes your data traffic through its servers to websites and services worldwide. ISPs also provide your router, manage DNS resolution, handle billing, and offer technical support. In the UK, the broadband market is highly competitive, with over 100 registered ISPs according to Ofcom's 2025 market report. However, the top five providers, BT, Sky, Virgin Media, Vodafone, and TalkTalk, account for around 85% of all residential connections. BT alone holds approximately 25% market share with over 8 million broadband subscribers. Sky serves roughly 5.77 million broadband customers, while Virgin Media has around 5.74 million cable subscribers. ISPs compete primarily on price, speed, customer service, and bundled extras such as television packages and mobile plans.

Network Owners vs Resellers

UK ISPs fall into two broad categories: network owners and resellers. Network owners build and maintain their own physical infrastructure. Virgin Media operates its own hybrid fibre-coaxial cable network covering 16 million premises. Hyperoptic builds and owns FTTP networks in apartment buildings and residential developments across 57 UK cities. CityFibre, which supplies broadband through ISP partners including Vodafone and TalkTalk, operates the third-largest full fibre network with over 3.5 million premises passed. Resellers, by contrast, lease capacity on someone else's network, typically Openreach. Sky Broadband, Plusnet, EE, and Zen Internet all deliver broadband over Openreach infrastructure. This means a Sky customer and a BT customer in the same street may share the same physical fibre cable, with the difference being the ISP's pricing, router, customer service, and traffic management policies.

How to Choose the Right ISP

Choosing an ISP involves balancing speed, price, contract length, and customer service quality. Start by checking which providers serve your address, as availability varies significantly by postcode. Ofcom's annual broadband satisfaction survey rates Zen Internet consistently highest for customer service, with 94% satisfaction in 2025. Sky scored 83% and BT 79%. For value, compare the total contract cost rather than just the monthly price. Look for setup fees, which range from free to £50, and note whether the provider applies annual price increases. Since Ofcom banned CPI-linked mid-contract rises from January 2025, many ISPs now apply fixed annual increases of £3 to £4 per month instead. EE Broadband bundles are attractive for EE mobile customers, offering inclusive data boosts and a combined bill. Consider whether you need a basic 36 Mbps connection or a faster package to support multiple devices.

Switching ISPs in the UK

Switching ISPs in the UK became significantly easier with the One Touch Switch process, which launched in April 2023 and completed over 1.6 million switches in its first year. You simply sign up with your new provider and they handle the cancellation with your old ISP. No phone calls to your existing provider are needed. The switch typically takes 10 to 14 working days. Under Ofcom rules, you face no loss of service during the transition, and automatic compensation of £6.10 per day applies if your new connection is delayed beyond the agreed activation date. Cuckoo Broadband operates on a rolling monthly contract with no exit fees, making it easy to try without commitment. Vodafone also offers 30-day rolling plans on selected packages. If your current provider applies early termination charges, these typically range from £5 to £15 per remaining month on the contract, though you are always entitled to a 14-day cooling-off period when signing any new deal.

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Frequently Asked Questions

What is the difference between an ISP and a network operator?

A network operator builds and maintains the physical cables and infrastructure. An ISP is the company you pay for broadband service. Some ISPs like Virgin Media own their network, while others like Sky lease Openreach infrastructure and add their own services on top.

Which is the biggest ISP in the UK?

BT is the largest UK ISP with approximately 25% market share and over 8 million broadband subscribers. Sky is second with around 5.77 million customers, followed closely by Virgin Media with approximately 5.74 million cable subscribers.

Can I use any ISP at my address?

Not necessarily. Availability depends on which networks serve your postcode. Most addresses can access Openreach-based providers like BT, Sky, and Plusnet. Virgin Media covers about 52% of premises. Alternative fibre networks have more limited but growing coverage.

How often can I switch ISPs?

You can switch at any time, though leaving mid-contract may incur early termination fees of £5 to £15 per remaining month. The One Touch Switch process makes switching straightforward. You always have a 14-day cooling-off period on new contracts.

Related Guides

Types of Broadband UK · Broadband Switching Checklist · How Long Does It Take to Switch Broadband · Broadband Contracts Explained

Methodology & Sources

Information in this guide is sourced from Ofcom market reports, Openreach coverage data, ISPreview.co.uk, provider websites and independent broadband research from Point Topic and Thinkbroadband. Prices and availability are checked monthly. Speed data reflects advertised average speeds from provider Key Facts documents.