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App signup verification code via WhatsApp API

Sends a WhatsApp authentication template with a one-time registration confirmation code in the message body and a copy-code button.

Use case overview

Sends a WhatsApp authentication template with a one-time registration confirmation code in the message body and a copy-code button. The user copies the code and completes signup in your mobile or web app.

Template example

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

Copy code
  • {{1}}
    one-time app registration confirmation code (digits)
  • “Copy code”
    button — fixed in the Meta template
WhatsApp Business API for app registration confirmation

When to use it

Reach for this scenario when a user starts registration in your mobile or web app and must confirm signup with a one-time code on WhatsApp before the account is activated, but no conversation exists yet — a free-text message is not allowed on cold start. It fits mobile and web app onboarding, teams replacing SMS-only OTP at registration, and developers, small teams, or agencies wiring signup confirmation into backend and IAM flows through the 1MSG API.

Confirm signup without an open chat
An approved authentication template opens the conversation on cold start, so a registration confirmation code reaches the user right after they submit signup details instead of waiting inside the 24-hour reply window.
Faster code entry in the app
One body variable carries the digit code and the copy-code button exposes the same value, so the user taps Copy code and pastes into your registration 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`.
Clear audit trail for signup
Delivery status is logged when the template goes out, so your backend can retry or alert on failures while it validates the code the user submits to activate the account.

Workflow

  1. Customer acts

    User submits registration in the app and requests confirmation.

    user action

  2. Capture event

    Backend generates a one-time code and resolves the user's WhatsApp number.

    phone: "+…"

  3. Build & send

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

    POST /sendTemplate

  4. Delivered

    User receives the WhatsApp message and copies or reads the code.

    delivered

  5. Status tracked

    Backend validates the submitted code and activates the account; delivery errors are handled per platform rules.

    status: "read"

WhatsApp Business API for app registration confirmation

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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Build for WhatsApp in hours
without infrastructure hassle