Overview

SMS is one channel in Twilio's Messaging platform. All channels — SMS, WhatsApp, RCS, Facebook Messenger — share the same messages.create() API. See twilio-messaging-overview for the full channel comparison and onboarding sequence.

For production SMS: Use a Messaging Service (messagingServiceSid) instead of a raw from number. It enables sender pool management, compliance toolkit, SMS pumping protection, link shortening, and message scheduling. See twilio-messaging-services.

Every outbound SMS requires a from Twilio number (or messagingServiceSid) and a to recipient — both in E.164 format.

Prerequisites

• Twilio account with an SMS-capable phone number — New to Twilio? See twilio-account-setup for signup, getting a number, and trial limitations
• Environment variables:
  • TWILIO_ACCOUNT_SID
  • TWILIO_AUTH_TOKEN — See twilio-iam-auth-setup for credential setup and best practices
• SDK: pip install twilio / npm install twilio

Quickstart

Python

import os
from twilio.rest import Client

client = Client(os.environ["TWILIO_ACCOUNT_SID"], os.environ["TWILIO_AUTH_TOKEN"])

message = client.messages.create(
    from_="+15017122661",   # Your Twilio number (E.164)
    to="+15558675310",      # Recipient (E.164)
    body="Your appointment is confirmed for tomorrow at 2pm."
)

print(message.sid)     # SMxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
print(message.status)  # queued | sent | delivered | failed

Node.js

const twilio = require("twilio");
const client = twilio(process.env.TWILIO_ACCOUNT_SID, process.env.TWILIO_AUTH_TOKEN);

const message = await client.messages.create({
    from: "+15017122661",
    to: "+15558675310",
    body: "Your appointment is confirmed for tomorrow at 2pm.",
});

console.log(message.sid);
console.log(message.status);

Key Patterns

Send MMS (with media)

Python

message = client.messages.create(
    from_="+15017122661",
    to="+15558675310",
    body="Here is your invoice.",
    media_url=["https://example.com/invoice.pdf"]
)

Node.js

const message = await client.messages.create({
    from: "+15017122661",
    to: "+15558675310",
    body: "Here is your invoice.",
    mediaUrl: ["https://example.com/invoice.pdf"],
});

Supported media types: images (JPEG, PNG, GIF), PDF, audio, video. Max 5 MB per message.

Send via Messaging Service (recommended for scale)

Use messagingServiceSid instead of from — Twilio picks the best sender automatically from your pool.

Python

message = client.messages.create(
    messaging_service_sid="MGxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
    to="+15558675310",
    body="Your order has shipped."
)

Node.js

const message = await client.messages.create({
    messagingServiceSid: "MGxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
    to: "+15558675310",
    body: "Your order has shipped.",
});

Track Delivery Status

Python

message = client.messages.create(
    from_="+15017122661",
    to="+15558675310",
    body="Hello!",
    status_callback="https://yourapp.com/sms-status"
)

Node.js

const message = await client.messages.create({
    from: "+15017122661",
    to: "+15558675310",
    body: "Hello!",
    statusCallback: "https://yourapp.com/sms-status",
});

Twilio POSTs to your URL at each transition: queued → sent → delivered (or failed/undelivered).

Response Fields

Common Errors

Messages Being Filtered or Blocked?

If your messages aren't being delivered, check these causes in order:

1. Unregistered sender (error 30034) — US 10DLC numbers must be registered. See twilio-compliance-onboarding
2. Spam filtered (error 30007) — Carrier flagged content. Check: opt-out language included? URL shorteners avoided? Content matches registered campaign?
3. Opted-out recipient (error 21610) — Recipient sent STOP. Do not retry. See twilio-compliance-traffic
4. Geo-permissions disabled (error 21408) — Enable the destination country in Console > Messaging > Settings > Geo Permissions. See twilio-security-hardening
5. SMS pumping (error 30450) — Artificial traffic detected. Whitelist known prefixes via Global Safe List. See twilio-messaging-services
6. Account suspended — Check Console for account status notifications. See twilio-account-setup

For delivery event tracking, set up StatusCallbacks or use twilio-debugging-observability.

CANNOT

• Cannot send without E.164 format — Both from and to must be + followed by country code and number
• Cannot send to unverified numbers on trial accounts — Upgrade to paid or verify recipient numbers first
• Cannot send MMS outside US, Canada, and Australia — MMS is only supported on US/CA/AU numbers; for international rich media use WhatsApp
• Cannot exceed 1,600 characters per message — Longer messages are automatically split into segments (each billed separately)
• Cannot prevent SMS pumping without a Messaging Service — Enable SMS pumping protection via Messaging Services to prevent artificial traffic inflation. See twilio-messaging-services

Next Steps

• Channel overview and onboarding guide: twilio-messaging-overview
• Receive inbound SMS and delivery status: twilio-messaging-webhooks
• Manage sender pools at scale: twilio-messaging-services
• US compliance for A2P traffic: twilio-compliance-onboarding
• Send via WhatsApp instead: twilio-whatsapp-send-message