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Two-factor authentication (2FA) via WhatsApp API

The scenario sends a WhatsApp authentication template with a one-time verification code when two-factor authentication is required after primary login.

Use case overview

The scenario sends a WhatsApp authentication template with a one-time verification code when two-factor authentication is required after primary login. The copy-code button lets the user paste the code into your verification screen without retyping digits from the chat.

Template example

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

Copy code
  • {{1}}
    one-time two-factor verification code (digits)
  • “Copy code”
    button — fixed in the Meta template
WhatsApp Business API for two-factor authentication

When to use it

Reach for this scenario when a user passes primary login with a password or SSO but must confirm identity with a second factor on WhatsApp before the session opens — there is usually no open chat yet, so a free-text message is not allowed on cold start. It fits login step-up after credentials, high-risk confirmations like transfers or admin access, and teams wiring 2FA into web apps, mobile apps, or IAM backends through the 1MSG API.

Second factor without an open chat
An approved authentication template opens the conversation on cold start, so the verification code reaches the user right after primary login instead of waiting inside the 24-hour reply window.
Faster code entry at step two
The digits appear as one body variable and the same value in the copy-code button parameter, so the user taps Copy code and pastes into your verification screen instead of retyping from another channel.
Fewer rejected API sends
Authentication templates require the OTP in both the message body and the copy-code button; supplying both avoids body-only requests that return `sent: false`.
Audit trail for login security
Delivery status is logged when the template goes out, so your backend can retry failed sends and keep a clear record while it validates the code before granting access.

Workflow

  1. Customer acts

    The user completes primary login; your backend decides that a second factor is required.

    user action

  2. Capture event

    A one-time verification code is generated and the user's WhatsApp number is resolved.

    phone: "+…"

  3. Build & send

    A template message is built with the code in the body and the same value in the copy-code button parameter.

    POST /sendTemplate

  4. Delivered

    The user receives the WhatsApp message and copies or reads the code.

    delivered

  5. Status tracked

    Your backend validates the submitted code and completes sign-in; delivery errors are handled per platform rules.

    status: "read"

WhatsApp Business API for two-factor authentication

Technical implementation

Prerequisites

  1. 1MSG API Key · How to get API Key
  2. WhatsApp Business account · How to Connect WABA
  3. WhatsApp Template · How to Approve WABA Template
  4. Customer opt-in · How to Manage Customers Consent

Code examples

#!/usr/bin/env bash
set -euo pipefail

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

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

TEMPLATE_NAME="___"                        # approved template name
TEMPLATE_NAMESPACE="___"                   # template namespace (required — send fails without it)
TEMPLATE_LANGUAGE="___"                    # template language code, e.g. "en"



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

PHONE_NORM="$(printf '%s' "$TEST_PHONE" | tr -cd '0-9')"

for pair in "CHANNEL_ID=$CHANNEL_ID" "API_TOKEN=$API_TOKEN" \
            "TEMPLATE_NAME=$TEMPLATE_NAME" "TEMPLATE_NAMESPACE=$TEMPLATE_NAMESPACE" \
            "TEMPLATE_LANGUAGE=$TEMPLATE_LANGUAGE" "TEST_PHONE=$TEST_PHONE" \
            "TEST_CODE=$TEST_CODE"; do
    val="${pair#*=}"
    if [ -z "$val" ] || [ "$val" = "___" ]; then
        echo "Missing configuration value: ${pair%%=*}" >&2
        exit 1
    fi
done

if [ -z "$PHONE_NORM" ]; then
    echo "Error: phone number has no digits after normalization" >&2
    exit 1
fi

URL="${API_BASE_URL%/}/${CHANNEL_ID}/sendTemplate"

# params carries body and button blocks.

# {{1}} otp code → ${TEST_CODE}
read -r -d '' PAYLOAD <<JSON || true
{
  "phone": "${PHONE_NORM}",
  "template": "${TEMPLATE_NAME}",
  "namespace": "${TEMPLATE_NAMESPACE}",
  "language": { "policy": "deterministic", "code": "${TEMPLATE_LANGUAGE}" },
  "params": [
    {
      "type": "body",
      "parameters": [
        { "type": "text", "text": "${TEST_CODE}" }
      ]
    },
    {
      "type": "button",
      "sub_type": "url",
      "index": "0",
      "parameters": [ { "type": "text", "text": "${TEST_CODE}" } ]
    }

  ]
}
JSON

RESPONSE="$(curl -s -w '\n%{http_code}' -X POST "$URL" \
    -H "Content-Type: application/json" \
    -H "Authorization: Bearer ${API_TOKEN}" \
    -d "$PAYLOAD")"

HTTP_CODE="$(printf '%s' "$RESPONSE" | tail -n1)"
BODY="$(printf '%s' "$RESPONSE" | sed '$d')"

case "$BODY" in
    *'"sent":true'*) ok=1 ;;
    *) ok=0 ;;
esac

if [ "$HTTP_CODE" -ge 200 ] && [ "$HTTP_CODE" -lt 300 ] && [ "$ok" -eq 1 ]; then
    echo "Message sent to client."
    echo "API response: $BODY"
else
    echo "Send failed. HTTP status: $HTTP_CODE" >&2
    echo "$BODY" >&2
    exit 1
fi

Response and delivery status

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 (looks like wamid.…) to correlate delivery callbacks.

200 OKResponse
{
  "sent": true,
  "message": "Sent to [email protected]",
  "description": "Message has been sent to the provider",
  "id": "wamid.HBgLMzgwNjM5..."
}
  • sent

    Accepted for sending — not yet on the customer's phone

  • id

    Store it; delivery callbacks and hookInfo are keyed on this

Delivery statuses and webhooks →

Common errors

StatusAPI responseCauseFix
200Message was not sent: template is not definednamespace, template or language is missing from the request body.Send all three. Take namespace and the exact template name from GET /templates; language is an object: {"policy": "deterministic", "code": "en"}.
200template name (…) does not exist in <language>The template is approved in a different language than the one requested.Use the exact language code the template was approved in (for example es_MX is not the same as es). Check it in GET /templates.
200Message was not sent: provide chatId, phone, bsuid, or usernameNo recipient the channel could resolve.Pass exactly one recipient: phone (country code plus number, digits only), chatId (for example [email protected]) or bsuid.

All error codes →

Common questions

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