tel: and sms: link generator

Always use the international form

tel:+442079460018 dials correctly from anywhere on earth. tel:02079460018 dials correctly only for someone already in the UK, and does something wrong or nothing at all for everyone else — which, on a website, is most of the people who will click it.

RFC 3966 addresses this directly: a number without a leading + is required to carry a phone-context saying which numbering plan it belongs to. This tool adds it, but the international form is still better.

Formatting is stripped, not preserved

Spaces, brackets and dashes are for humans reading the page, not for the dialler. Type the number however you like; what goes into the link is digits, an optional leading +, and nothing else.

Extensions

;ext= is the standard way to express an extension behind a phone tree. Support varies: some diallers dial it automatically after connecting, and some simply display it. It is still the right thing to put in the URI.

SMS bodies

sms:+15551234567?body=… is what RFC 5724 specifies. Older iOS versions wanted an ampersand instead of a question mark, and some Android SMS apps ignore the body entirely. The standard form is what this emits — a prefilled message that does not arrive is a minor failure, and a link that opens nothing is not.

A prefilled message is never sent automatically. The user sees it and presses send.