Twilio
Send SMS, make calls, or verify phone numbers without touching a telecom carrier directly. The API you reach for the moment "notify the user by text" shows up in a spec.
What is Twilio?
Twilio is a communications API platform: SMS, voice calls, WhatsApp messaging, phone number verification, and video, all exposed as REST APIs and SDKs so you never have to negotiate directly with telecom carriers. It's been the default answer to "how do I send a text message from my app" for over a decade, with enough surrounding tooling (Verify, Lookup, Studio for visual flow building) that most communication needs beyond a single API call are covered too.
Key features
- SMS and voice APIs that work across a huge number of countries and carriers without separate carrier relationships
- Twilio Verify handles OTP/2FA flows (send code, check code) without building that logic yourself
- Programmable Voice for building call flows, IVRs, and click-to-call features
- Lookup API to validate and get metadata (carrier, line type) on phone numbers before you send anything
- Mature SDKs across nearly every language, plus a large library of code samples for common flows
Who it's for
Any app that needs to reach users by SMS, voice, or WhatsApp, from a simple OTP flow to a full call center product. Pricing and per-message costs mean it's worth comparing against narrower providers if all you need is transactional SMS at high volume.
Pricing
Pay-as-you-go pricing per message, call minute, or verification, with costs varying significantly by country and channel. No flat subscription tier for the core APIs.