Need a WhatsApp OTP API or WhatsApp authentication API for login and signup? Messlo verifies phone numbers on the official WhatsApp Business API without sending a paid Authentication OTP template on every login. REST API, Node SDK, Next.js package, and webhooks—0% Meta markup.
India OTP comparisons use ₹0.115/verification as a typical benchmark—actual Meta Authentication charges may differ. See cost section for details.
Replace costly WhatsApp OTP flows with a user-initiated LOGIN path—faster UX and lower Meta Authentication spend.
OTP benchmark (India)
Meta Authentication rate (₹0.115 per verification in India)—Login with WhatsApp avoids that outbound OTP template.
First login live
Create a Login app, copy API key, wire start → verify-token on your backend.
Messlo on Vyapar
Vyapar platform cost from ₹0.02/login—below ₹0.115 Meta Authentication OTP in your currency.
Messlo Meta markup
Pay Meta at official rates. Messlo never inflates WhatsApp conversation fees.
Guide
Clear answers for teams searching WhatsApp OTP API, WhatsApp authentication API, and phone verification on the Business API.
A WhatsApp OTP API sends one-time passwords using Meta Authentication templates on the WhatsApp Business API. You pay Meta per verification (rates vary by country). Businesses use it for login, signup, and step-up verification when users already have WhatsApp installed.
Login with WhatsApp is a WhatsApp login API where the user taps to open WhatsApp and sends a pre-filled LOGIN message—you verify their phone on your backend. It avoids outbound Authentication OTP template charges on each login while still using the official Cloud API.
Messlo acts as your WhatsApp phone verification API layer: start a session, confirm the number via Meta webhooks, receive a signed verification token, then create your app session. Works for web, SaaS, and mobile (REST today; Flutter SDK coming soon).
Create a Login app in Messlo → copy API key → POST /v1/auth/whatsapp/start → user completes LOGIN in WhatsApp → poll or SSE → POST verify-token on your server. Use @getmesslo/messlo-node-sdk and @getmesslo/messlo-whatsapp-login for production Next.js apps.
Meta Authentication templates bill about ₹0.115 per verification in India. Login with WhatsApp uses a user-initiated message instead—see Messlo plan cost per login below.
Lower cost than WhatsApp OTP
Outbound WhatsApp OTP templates use Meta’s official Authentication rate for India (about ₹0.115 per verification in INR). Login with WhatsApp lets the user message you first—no Authentication OTP template—so you avoid that per-OTP charge. Messlo adds 0% markup on Meta fees.
Plan prices convert to your selected currency. Allocated Messlo cost per login stays below Meta’s India Authentication OTP rate (₹0.115) at the included session cap.
At 10,000 logins/month (India): OTP Meta ≈ ₹1,150 vs Vyapar Messlo platform ≈ ₹200—about ₹950 less on platform fees alone (₹0.115 Meta Authentication benchmark).
At 10,000 logins/month in India, Authentication OTP Meta cost alone is about ₹1,150 (₹0.115 × logins). Login with WhatsApp avoids that OTP line item.
For India, OTP comparisons use ₹0.115 per verification as a typical Authentication OTP template benchmark—not Meta’s full published Authentication conversation rate, which can differ. Figures are illustrative only; your actual Meta invoice may vary by template, volume, and billing rules.
Meta Authentication rates from Meta’s rate card for India (INR). Messlo plan prices are billed in INR and converted using live FX. Messlo never marks up Meta WhatsApp fees. Logins above your plan session cap require an upgrade.
From Messlo dashboard apps to server-side token verification—production-ready on the official Business API.
Official Flutter package on the roadmap. Today use Web Login apps or REST from any mobile stack—same API keys, wa.me links, and poll/SSE status.
QR or tap-to-open WhatsApp login for browsers—same verify-token flow on your backend after Messlo confirms the number.
Get whatsapp.auth.verified events on your URL with HMAC secrets—multi-environment endpoints per app.
Prefer push over polling? Subscribe to login events or poll /status until you receive the verification token.
product_wa_login_block_shared_number_desc
Messlo returns a signed JWT; your backend validates once and creates your own app session—never trust client-only checks.
Mobile apps, SaaS dashboards, and onboarding flows—especially where OTP costs add up.
2×
faster sign-in
Mobile apps
One-tap WhatsApp login without SMS OTP fallbacks—use Web Login or REST today; Flutter SDK coming soon.
−OTP
Auth template fees
SaaS
Replace email magic links or costly OTP with WhatsApp identity on the official API.
1
message to verify
Onboarding
Messlo itself uses the same flow—Sign up with WhatsApp on register/login without a separate phone OTP vendor.
10k
logins example
Cost control
At 10k logins/month, ₹0.115 OTP (India) adds up fast in Meta Authentication fees—Login avoids that per-verification template charge.
Create an app, integrate start/status, verify token on your server, ship to production.
Step 1
Pick Web (Flutter SDK soon), tenant or Messlo number, copy API key and webhook secret once.
Step 2
POST /v1/auth/whatsapp/start from your server with X-API-Key; expose verify-token route.
Step 3
Open waLink, send LOGIN from your phone, confirm verify-token returns phone and name.
Step 4
Users sign in with WhatsApp; you own sessions, analytics, and support flows after verification.
Your app starts a session; the user confirms in WhatsApp; your server verifies the token.
1
API start call
~10s
Typical verify time
1×
Single-use token
Example flow
Messlo verifies WhatsApp identity only—you issue your own application session.
Cost comparison
Meta Authentication OTP rates vary by market—select your currency in the header and compare official Meta vs Messlo platform cost.
Login with WhatsApp
User-initiated
WhatsApp OTP
Auth template
Full developer docs: Integration guide →
Meta Tech Provider infrastructure with signed tokens and webhook HMAC—built for regulated apps.
Verification tokens are one-time; replay attempts fail on verify-token.
Rotate webhook secrets per Login app without affecting other integrations.
Transparent monthly login session caps—upgrade as you grow.
Integration guide, API reference, and messlo-mcp tools for Cursor.
Create your first Login app free—WhatsApp phone verification API with lower platform cost than per-OTP templates.
Get started freeAnswers for WhatsApp OTP API for business, WhatsApp login API pricing, WABA setup, and Login with WhatsApp integration.