United Kingdom phone number validator
How the phone number format works
- Format
- United Kingdom phone number in national or international (+44) format
- Example
- +447400123456
Things to watch for
- Accepts national or international (E.164, e.g. +44...) format
- Validated with Google's libphonenumber; confirms the number is possible/valid for this country, not that it is currently assigned or reachable
^[+]?[0-9 ()\-]{6,}$A UK phone number is 11 digits in national form, starting with 0 — 07 for mobile (07400 123456), or a regional landline code such as 020 for London or 0121 for Birmingham, where the area-code length itself varies between 2 and 4 digits after the 0. That leading 0 is a trunk prefix, dropped the moment +44 is added: a mobile written as 07400 123456 domestically becomes +447400123456 internationally — 10 digits after the country code.
How this validator works
Enter the number in national form (07400123456) or full international form (+447400123456); this tool checks the digit count, the 0-prefix, and the mobile or area-code pattern against the UK’s real numbering plan using Google’s libphonenumber, entirely client-side. Because UK landline area codes vary in length, the validator checks the specific area-code-plus-local-number pattern rather than one fixed rule, while mobile numbers follow a single consistent 07-plus-9-digit shape.
What a pass doesn’t tell you
A pass confirms the number matches a real UK mobile or landline shape — it doesn’t confirm the SIM is active or the landline connected. UK mobile numbers are recycled by networks after long periods of inactivity, so a correctly-shaped number is not proof of a live line.
Scope: catch a missing digit, wrong area code length, or a leftover 0 after +44 before a UK number reaches a form or SMS gateway — not confirmation it rings through.
Content last reviewed 2026-07-07.
phone number FAQ
Do I need to remove the leading 0 for a UK number in +44 format?
Yes. The 0 in 07400 123456 is a national trunk prefix, dropped as soon as +44 is added — the correct form is +447400123456, ten digits after the country code, with no 0 in between.
Why do UK landline area codes have different lengths?
The UK's numbering plan assigns shorter area codes to larger cities and longer ones to smaller areas — London's 020 has 2 digits after the 0, while some rural codes run to 4 — so the local-number length adjusts to keep the total digit count consistent.
Does a valid UK mobile check mean the number is reachable?
No. It only confirms the digits match a real UK mobile pattern — 07 plus 9 digits — not that the SIM is currently active, since UK networks regularly recycle mobile numbers after disconnection.