Nigerian phone number formats for developers

What is the correct format for a Nigerian phone number?

In international E.164 form it is +234 followed by ten digits: +2348012345678. The local form of the same number is 08012345678 - the same ten digits with a national trunk prefix 0 in front of them. Converting between the two is simply removing or adding that leading 0.

How the ten digits are structured

A Nigerian mobile number is a three-digit network prefix followed by seven subscriber digits. The prefix always begins 70, 71, 80, 81, 90 or 91 - which is why a validator can reject a great deal of rubbish cheaply, before any network is involved.

^\+?234[789][01]\d{8}$

• 234 - the Nigerian country code.
• [789][01] - the first two digits of the mobile prefix: 70, 71, 80, 81, 90 or 91.
• Eight further digits, completing the ten-digit national number.
• The leading + is optional on input; Sendozi normalises it back on.

Normalising a number

1. 1

   Strip everything that is not a digit or a leading plus

   Spaces, hyphens, brackets and non-breaking spaces pasted from spreadsheets.

2. 2

   Replace a leading 00 with +

   The international dialling prefix in E.164 form is +.

3. 3

   If it starts with 0 and is 11 digits, replace the 0 with +234

   This is the common Nigerian local form.

4. 4

   If it starts with 234, prefix +

   Already international, just missing the plus.

5. 5

   If it is 10 digits starting 7, 8 or 9, prefix +234

   A number entered without the trunk 0, which happens on forms that show a +234 prefix beside the field.

6. 6

   Validate the result against the pattern

   Reject anything that does not match, rather than sending it and paying for the failure.

const NIGERIAN_MOBILE = /^\+234[789][01]\d{8}$/;

export function normaliseNigerianMobile(input: string): string | null {
  let value = input.trim().replace(/[\s()\-.]/g, "");

  if (value.startsWith("00")) value = `+${value.slice(2)}`;
  if (/^0\d{10}$/.test(value)) value = `+234${value.slice(1)}`;
  else if (/^234\d{10}$/.test(value)) value = `+${value}`;
  else if (/^[789][01]\d{8}$/.test(value)) value = `+234${value}`;

  return NIGERIAN_MOBILE.test(value) ? value : null;
}

import re

NIGERIAN_MOBILE = re.compile(r"^\+234[789][01]\d{8}$")
_STRIP = re.compile(r"[\s()\-.]")


def normalise_nigerian_mobile(raw: str) -> str | None:
    value = _STRIP.sub("", raw.strip())

    if value.startswith("00"):
        value = "+" + value[2:]
    if re.fullmatch(r"0\d{10}", value):
        value = "+234" + value[1:]
    elif re.fullmatch(r"234\d{10}", value):
        value = "+" + value
    elif re.fullmatch(r"[789][01]\d{8}", value):
        value = "+234" + value

    return value if NIGERIAN_MOBILE.fullmatch(value) else None

<?php

function normaliseNigerianMobile(string $raw): ?string
{
    $value = preg_replace('/[\s()\-.]/', '', trim($raw));

    if (str_starts_with($value, '00')) {
        $value = '+' . substr($value, 2);
    }

    if (preg_match('/^0\d{10}$/', $value)) {
        $value = '+234' . substr($value, 1);
    } elseif (preg_match('/^234\d{10}$/', $value)) {
        $value = '+' . $value;
    } elseif (preg_match('/^[789][01]\d{8}$/', $value)) {
        $value = '+234' . $value;
    }

    return preg_match('/^\+234[789][01]\d{8}$/', $value) ? $value : null;
}

-- Normalise an existing column in place, then keep the constraint.
update contacts
set phone = '+234' || right(regexp_replace(phone, '[^0-9]', '', 'g'), 10)
where phone !~ '^\+234[789][01][0-9]{8}$'
  and right(regexp_replace(phone, '[^0-9]', '', 'g'), 10) ~ '^[789][01][0-9]{8}$';

alter table contacts
  add constraint contacts_phone_e164
  check (phone ~ '^\+234[789][01][0-9]{8}$');

Validation traps that cost money

One more habit is worth adopting: normalise on the way in, not on the way out. If every entry point - signup form, CSV import, admin panel, partner API - writes E.164, then everything downstream can assume it. Normalising at send time means every consumer of the data has to remember to do it.

When to reach for a library

For a Nigeria-only product, the regular expression above is sufficient and has no dependency cost. If you also handle other countries, use Google's libphonenumber (or a port of it) rather than accumulating per-country regexes - it tracks numbering plan changes, which a hand-written pattern will not.