WhatsApp Business API for phone number verification code

Use case overview

Delivers a one-time code via WhatsApp authentication template when the user adds or changes a phone number. Copy-code button lets them paste the code in your profile form.

Template example

{{1}} is your verification code. For your security, do not share this code with anyone.

[Copy code]

Authentication templates require the OTP in two API places — body and copy-code button. Body-only sends return sent: false.

Variables and purpose

• {{1}} — one-time phone verification code (digits)

Filled-in example

123456 is your verification code. For your security, do not share this code with anyone.

[Copy code]

When to use it

• profile phone change
• account linking
• compliance

Business value

• User submits a new phone number for verification
• System generates a one-time code and resolves the recipient phone
• Authentication template is built with the code in body and copy-code button
• WhatsApp message is delivered to the user
• User submits the code; backend validates ownership and saves the new number

Workflow

1. User enters a new phone number and requests verification.
2. Backend generates a code and sends the authentication template.
3. User copies the code from WhatsApp and submits it.
4. Backend validates and persists the verified number.
5. Delivery progress is reported asynchronously — typically sent, then delivered (or failed/undelivered).
6. Your system receives status via webhook (hooks[]) or polls GET …/hookInfo?messageId=<id> and handles failures if needed.

Technical implementation

Prerequisites

• Approved authentication template with copy-code button on your 1MSG channel.
• New phone number in international format (without + and spaces).
• Backend generates OTP, sends body + button params, validates on submit.

Code examples

#!/usr/bin/env node

// === Configuration (replace "___" placeholders) ===

const API_BASE_URL = "https://api.1msg.io"; // production 1MSG API base URL
const CHANNEL_ID = "___";                   // channel ID from 1MSG dashboard
const API_TOKEN = "___";                    // channel JWT token (Bearer)

const TEMPLATE_NAME = "___";                // approved template name
const TEMPLATE_NAMESPACE = "___";           // template namespace (422 without it)
const TEMPLATE_LANGUAGE = "___";            // template language code, e.g. "en"



// === Test data ===
const TEST_PHONE = "___";            // client phone in international format
const TEST_CODE = "___";    // {{1}} otp code

function normalizePhone(phone) {
  return String(phone).replace(/\D/g, "");
}

function assertConfigured(values) {
  for (const [key, value] of Object.entries(values)) {
    if (value === "___" || value === "" || value === undefined || value === null) {
      throw new Error(`Missing configuration value: ${key}`);
    }
  }
}

async function sendTemplateMessage({ phone, code }) {
  assertConfigured({
    CHANNEL_ID,
    API_TOKEN,
    TEMPLATE_NAME,
    TEMPLATE_NAMESPACE,
    TEMPLATE_LANGUAGE,
    phone,
    code,
  });

  const url = `${API_BASE_URL}/${CHANNEL_ID}/sendTemplate`;

  // params carries body and button blocks.
  const requestBody = {
    phone: normalizePhone(phone),
    template: TEMPLATE_NAME,
    namespace: TEMPLATE_NAMESPACE,
    language: {
      policy: "deterministic",
      code: TEMPLATE_LANGUAGE,
    },
    params: [
      {
        type: "body",
        parameters: [
          { type: "text", text: String(code) }, // {{1}} otp code
        ],
      },
      {
        type: "button",
        sub_type: "url",
        index: "0",
        parameters: [{ type: "text", text: String(code) }],
      },
    ],
  };

  const res = await fetch(url, {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      Authorization: `Bearer ${API_TOKEN}`,
    },
    body: JSON.stringify(requestBody),
  });

  const raw = await res.text();
  let data;
  try {
    data = JSON.parse(raw);
  } catch {
    data = null;
  }

  if (!res.ok || !data || data.sent !== true) {
    console.error("Send failed. API response:");
    console.error(raw);
    process.exit(1);
  }

  console.log("Message sent to client.");
  console.log("API response:", raw);
  return data;
}

if (require.main === module) {
  sendTemplateMessage({
    phone: TEST_PHONE,
    code: TEST_CODE,
  }).catch((err) => {
    console.error("Execution failed:", err.message);
    process.exit(1);
  });
}

module.exports = { sendTemplateMessage };

Immediate API response (synchronous)

• HTTP 2xx and JSON "sent": true mean 1MSG accepted the message for sending — not that it already reached the customer's phone.
• Save the `id` field from the response (value looks like wamid.…). Use it to correlate delivery callbacks or polling.
• The response may also include message and description — informational only.

Delivery status (asynchronous)

• Register a webhook (POST …/webhook) so 1MSG POSTs delivery updates to your HTTPS endpoint in a separate `hooks[]` payload (sent, delivered, read, or failed/undelivered when applicable).
• Optionally poll: GET {base}/{channel}/hookInfo?messageId=<id from sendTemplate>.
• In practice, delivery often completes within a few seconds — but that is not guaranteed by the API contract.

Common errors

• Invalid or non-normalized phone number
• Unapproved or missing template name / namespace
• No customer opt-in for WhatsApp business messages
• Template variable count mismatch (422 from API)
• Delivery failure — check status webhook and retry policy

FAQ

• Do I need an approved template? Yes — cold-start WhatsApp messages require a Meta-approved template.
• Can I customize the message text? Body variables are dynamic; fixed text and button labels are set in the Meta template.
• How do I check delivery? sent: true only confirms acceptance. Track delivery via webhook hooks[] or GET …/hookInfo?messageId=<id>.
• What if the message is not delivered? Log the failed/undelivered hook, verify opt-in and template status, then retry or fall back to another channel.
• Can I connect this to my CRM or backend? Yes — trigger the API call from your platform webhook or event handler.

Related

• Knowledge base
• Creating a template
• Sending a template
• SDK