0171

0171 is a former telephone area code in the United Kingdom. It was used for Inner London as part of the London numbering plan, replacing the older 071 code during the late 20th century as part of a broader reorganization of UK area codes. The change was intended to standardize and expand dialing capacity across the capital.

In the wider context of the UK numbering system, London underwent a significant modernization during the Big Number Change, completed around 2000. As part of that transition, London area codes were consolidated under the 020 prefix. Inner London numbers previously carried 0171 were migrated to 0207, with some locations moving to 0208 depending on geographic assignment. The 0171 code itself was retired from use for new numbers, and existing 0171 numbers were ported to the new 020-based prefixes where possible.

Today, 0171 is no longer assigned to new telephone numbers and is primarily encountered in historical references, legacy documents, or older records. The transition to the 020-based system reduced the number of distinct area codes in London and simplified dialing patterns within the capital and across the country. The 0171 code remains a part of the historical record of the UK’s evolving telephone numbering system.