Twilio

Twilio is a cloud communications platform providing APIs for SMS, voice calls, video conferencing, email, and messaging channels like WhatsApp. It enables developers to embed communication features directly into applications using programmable APIs rather than building telephony infrastructure from scratch. A few API calls can send an SMS notification, initiate a phone call, or verify a user's phone number.

Common integrations include two-factor authentication via SMS or voice codes, appointment reminders, order notifications, customer support phone systems, and in-app video chat. Twilio Verify handles phone verification flows. The programmable nature means communication logic can be triggered by application events, personalized per user, and tracked through webhooks that report delivery status. For web developers building applications that need to communicate with users through channels beyond the browser, Twilio provides the infrastructure that handles carrier relationships, global routing, and compliance requirements.