Make a link that opens a WhatsApp chat with your number, with a message already typed. Put it on your website, Instagram bio, business card or email.
Type it the way you normally dial it. The country code is added for you.
Everything is built in your browser. Your number and message are never sent to us. The link opens WhatsApp on phones and WhatsApp Web or the desktop app on a computer, for personal and WhatsApp Business accounts. The number must be a real WhatsApp number. Keep the message short: very long messages may be cut off or fail to open on some phones. Never share a link that contains private information.