Klaviyo requires that phone numbers are entered in international format (E.164).
E.164 is the international telephone numbering plan that ensures each device on the PSTN has globally unique number.
This number allows phone calls and text messages can be correctly routed to individual phones in different countries. E.164 numbers are formatted [+] [country code] [subscriber number including area code] and can have a maximum of fifteen digits.
On the front-end all “tel” input field in the form will have an input mask. Here is an example of how it works.
Note: Any contact form on the screen with a tel field will have the input mask applied.