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Telephone numbers in the United Kingdom

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Telephone numbers are of variable length. Local numbers are supported from landlines. Numbers can be dialled with a '0'-lead prefix that denotes either a geographical region or another service. Mobile phone numbers have distinct prefixes that are not geographic, and are portable between providers.

Structure

All mobile numbers, nearly all geographic numbers, and nearly all non-geographic numbers have ten national (significant) digits after the trunk code 0. The overall structure of the UK's National Numbering Plan is:

A short sample of geographic numbers, set out in the officially approved (Ofcom) number groups:

In the United Kingdom, the "area code" was historically referred to as a "subscriber trunk dialling code" (STD code) or a "dialling code". United Kingdom area codes are two, three, four or, exceptionally, five digits long (after the initial zero). Regions with shorter area codes, typically large cities, permit the allocation of more telephone numbers as the local number part has more digits. Local customer numbers are four to eight digits long. The total number of digits is ten or, very rarely, nine.

The code allocated to the largest population is (020) for London. The code allocated to the largest area is (028) for all of Northern Ireland. The UK Numbering Plan also applies to three British Crown dependencies – Guernsey, Jersey, and the Isle of Man – even though they are not part of the UK, these countries are closely related.

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