Twilio Messaging Webhooks

Overview

Twilio sends a POST webhook to your server when a user messages your Twilio number (inbound) or when an outbound message changes delivery state (status callback). Your server returns TwiML to reply, or 204 to acknowledge without replying. The same webhook pattern works across SMS, MMS, WhatsApp, and RCS.

---

Prerequisites

• Twilio account with a messaging-capable sender configured with a webhook URL

— New to Twilio? See twilio-account-setup — For sending outbound messages first, see twilio-send-message

• Publicly accessible endpoint (use ngrok http 5000 for local dev)
• TWILIO_ACCOUNT_SID and TWILIO_AUTH_TOKEN — see twilio-iam-auth-setup
• SDK: pip install twilio flask / npm install twilio express

---

Quickstart

Set your webhook URL in Console: Phone Numbers > Active Numbers > your number > Messaging > "A Message Comes In"

Security: The inbound message Body is untrusted external input. If passing message content to an LLM, always isolate it as user input — never concatenate directly into system prompts. Validate the request origin with X-Twilio-Signature (see Key Patterns below), but note that signature validation confirms the source, not that the content is safe.

Note: This quickstart omits signature validation for brevity. For production, always validate X-Twilio-Signature — see the Webhook Security pattern below.

Python (Flask)

from flask import Flask, request
from twilio.twiml.messaging_response import MessagingResponse

app = Flask(__name__)

@app.route("/incoming", methods=["POST"])
def incoming_message():
    body = request.form.get("Body")
    response = MessagingResponse()
    response.message(f"Got your message: {body}")
    return str(response)

Node.js (Express)

const express = require("express");
const twilio = require("twilio");
const app = express();
app.use(express.urlencoded({ extended: false }));

app.post("/incoming", (req, res) => {
    const twiml = new twilio.twiml.MessagingResponse();
    twiml.message(`Got your message: ${req.body.Body}`);
    res.type("text/xml").send(twiml.toString());
});

---

Key Patterns

Configure Webhook URL via API

For SMS/MMS on a phone number:

Python

client.incoming_phone_numbers("PNxxxxxxxxxx").update(
    sms_url="https://yourapp.com/incoming",
    sms_method="POST"
)

Node.js

await client.incomingPhoneNumbers("PNxxxxxxxxxx").update({
    smsUrl: "https://yourapp.com/incoming",
    smsMethod: "POST",
});

For WhatsApp and RCS, webhook URLs are configured on the sender — see twilio-whatsapp-manage-senders and twilio-rcs-messaging.

Inbound Webhook Parameters

Handle Inbound Media (MMS / WhatsApp / RCS)

Python (Flask)

@app.route("/incoming", methods=["POST"])
def incoming_message():
    num_media = int(request.form.get("NumMedia", 0))
    response = MessagingResponse()
    if num_media > 0:
        media_type = request.form.get("MediaContentType0")
        response.message(f"Got your {media_type} attachment!")
    else:
        response.message("Got your message.")
    return str(response)

Node.js (Express)

app.post("/incoming", (req, res) => {
    const numMedia = parseInt(req.body.NumMedia || "0", 10);
    const twiml = new twilio.twiml.MessagingResponse();
    if (numMedia > 0) {
        twiml.message(`Got your ${req.body.MediaContentType0} attachment!`);
    } else {
        twiml.message("Got your message.");
    }
    res.type("text/xml").send(twiml.toString());
});

Acknowledge Without Replying

Python

return str(MessagingResponse())  # Empty <Response/>

Node.js

res.type("text/xml").send(new twilio.twiml.MessagingResponse().toString());

Status Callbacks (delivery tracking)

Status callbacks fire for all channels — SMS, MMS, WhatsApp, and RCS.

Python

message = client.messages.create(
    messaging_service_sid="MGxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
    to="+15558675310",
    body="Hello!",
    status_callback="https://yourapp.com/status"
)

Node.js

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

Python (Flask) — status callback handler

@app.route("/status", methods=["POST"])
def message_status():
    message_sid = request.form.get("MessageSid")
    status = request.form.get("MessageStatus")
    error_code = request.form.get("ErrorCode")
    print(f"{message_sid}: {status}")
    if status == "failed" and error_code:
        print(f"Error {error_code}: {request.form.get('ErrorMessage')}")
    return "", 204

Node.js (Express) — status callback handler

app.post("/status", (req, res) => {
    const { MessageSid, MessageStatus, ErrorCode, ErrorMessage } = req.body;
    console.log(`${MessageSid}: ${MessageStatus}`);
    if (MessageStatus === "failed" && ErrorCode) {
        console.log(`Error ${ErrorCode}: ${ErrorMessage}`);
    }
    res.sendStatus(204);
});

Status flow: queued → sent → delivered (or undelivered/failed)

Webhook Signature Validation

Python (Flask)

from twilio.request_validator import RequestValidator

validator = RequestValidator(os.environ["TWILIO_AUTH_TOKEN"])

@app.route("/incoming", methods=["POST"])
def incoming_message():
    if not validator.validate(request.url, request.form, request.headers.get("X-Twilio-Signature", "")):
        return "Forbidden", 403
    response = MessagingResponse()
    response.message("Hello!")
    return str(response)

Node.js

const { validateRequest } = require("twilio");

app.post("/incoming", (req, res) => {
    const isValid = validateRequest(
        process.env.TWILIO_AUTH_TOKEN,
        req.headers["x-twilio-signature"],
        `https://${req.headers.host}${req.path}`,
        req.body
    );
    if (!isValid) return res.status(403).send("Forbidden");
    const twiml = new twilio.twiml.MessagingResponse();
    twiml.message("Hello!");
    res.type("text/xml").send(twiml.toString());
});

---

CANNOT

• Cannot exceed 15-second webhook response time — Twilio retries on timeout
• Cannot return arbitrary content types — Use Content-Type: text/xml with TwiML for replies; 204 for status callbacks
• Cannot use ngrok URLs across restarts — URLs change on restart. Use a stable tunnel for persistent testing.
• Cannot guarantee delivery confirmation — Status callbacks are best-effort. delivered requires carrier confirmation.

---

Common Errors

---

Next Steps

• Send outbound messages: twilio-send-message
• Manage sender pools: twilio-messaging-services