Send and verify one-time passcodes over SMS, WhatsApp and Telegram.
Free
One server, in authentication & identity. Send and verify one-time passcodes over SMS, WhatsApp and Telegram.
Authentication & Identity
Send and verify one-time passcodes over SMS, WhatsApp and Telegram.
The rest either hold an API key issued by the publisher or ask for nothing.
Listed without a verification tick. Read the listing before installing.