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The international format
Every phone number can be written as + then the country code, then the national number without its trunk prefix. This is the format apps store, often called E.164. Example: a UK mobile written locally as 07700 900123 becomes +44 7700 900123.
The leading 0
Many countries add a 0 in front of numbers dialled inside the country: the UK, Germany, France, the Netherlands, Ireland, Australia and others. That 0 is not part of the international number. Typing +44 07… or +49 0151… is the most common reason a valid number gets rejected.
Countries without a 0
- United States and Canada (+1): 10 digits, no 0
- Spain (+34) and Poland (+48): 9 digits, no 0
- When in doubt, paste the number exactly as your dashboard shows it after the country code
When the app already shows the code
If the form has a country picker that already shows +44 or +1, type only the national part — without the code and without the 0.