WhatsApp Business API vs SMS in India: Cost, DLT, OTP and When to Use Each

For years, SMS was the only way an Indian business could reach every customer's phone: order updates, bank alerts, OTPs, sale announcements. Today most of those customers also use WhatsApp, and the WhatsApp Business API lets a business send them the same messages with images, buttons and a real two-way conversation. That does not make SMS obsolete. This guide compares the two honestly — rules, cost, OTPs and results — so you can decide what goes where.

WhatsApp vs SMS at a glance

How SMS works in India: DLT registration

Every business that sends bulk or commercial SMS in India falls under TRAI's Telecom Commercial Communications Customer Preference Regulations (TCCCPR), 2018, which operators enforce through a blockchain-style register called DLT (Distributed Ledger Technology). According to TRAI's own advice to senders, you must complete four steps before a single message goes out:

1. Principal entity registration — your business registers on an operator's DLT portal.
2. Header registration — the sender ID customers see, an alphanumeric string of up to 11 characters.
3. Content template registration — every message format, with its fixed text and variable parts, is registered in advance.
4. Consent registration — for promotional messages, customer consent is taken through a registered consent template.

Each SMS is checked (“scrubbed”) against these records as it passes through the operator. If the header, template or consent does not match, the message is dropped. Since TRAI's direction of August 2024, SMS containing URLs, APK links, OTT links or call-back numbers that you have not whitelisted are blocked too — so a new tracking link in a campaign can silently stop delivery.

WhatsApp has its own equivalent discipline: every business-initiated message is an approved template, and customers must have opted in. The difference is that WhatsApp approval happens once per template with Meta, and there is no separate header or operator portal. Our guides to message templates and WhatsApp opt-in cover those rules.

WhatsApp Business API vs SMS marketing: cost comparison

The two channels are priced in different units, which is why a simple “per message” comparison often misleads.

How SMS is priced

• Per SMS unit, from a provider. Businesses usually buy SMS credits or pay per SMS from an SMS gateway. Prices vary with volume, route (promotional or service) and provider.
• Length changes the count. One SMS holds 160 plain-English characters; longer messages are split into several parts, each billed. Hindi and other Indian scripts use Unicode, which fits far fewer characters per part — so a regional-language message can cost two or three SMS.
• Operator charges are passed on. Operators levy DLT-related charges on commercial SMS, which providers typically fold into their rate. Ask for an all-inclusive price.
• Submitted or delivered? Ask whether you are billed per SMS submitted or per SMS delivered. The two are not the same bill.

How WhatsApp is priced

Meta charges per delivered template message, by category and the recipient's country. For customers in India, Meta's rate card (effective 1 July 2026) lists ₹0.8631 per marketing message and ₹0.115 per utility or authentication message, before 18% GST. Messages that fail to deliver are not charged. Your provider adds a platform fee — on wbm.link that is ₹999 per connected number per month, with unlimited team members.

Two things usually decide the comparison. First, marketing on WhatsApp costs noticeably more per message than utility or OTP messages, so promotional volume is where SMS can still look cheaper on paper. Second, WhatsApp messages carry more — a product image, a “Buy now” button, a reply in the same chat — so compare cost per result (orders, bookings, payments), not only cost per send. For a full breakdown, read WhatsApp Business API pricing in India or try the pricing calculator.

Is WhatsApp Business API better than SMS for OTP?

For many apps, WhatsApp is a good first choice for OTPs — but rarely the only one.

OTP on WhatsApp: authentication templates

• OTPs are sent as authentication templates with fixed wording set by Meta — the code, an optional “do not share” warning and an optional expiry time.
• Templates can carry a copy code button, or one-tap autofill and zero-tap options that pass the code to your Android app, so the customer does not type it.
• In India, authentication messages are charged at ₹0.115 per delivered message. A higher authentication-international rate applies only to businesses whose primary location is outside India and that cross Meta's volume threshold (more than 750,000 business-initiated messages in 30 days to countries with that rate).
• The customer needs WhatsApp and an internet connection at that moment.

OTP on SMS

• Reaches any mobile number, with or without data, on any phone.
• Needs a registered DLT header and OTP content template; unregistered formats are dropped.
• Phones can often pick up the code from the SMS for the customer — on iPhone it is suggested above the keyboard; on Android, apps can read it with the customer's permission.
• Priced per SMS by your provider, with the same questions about delivered versus submitted.

The common pattern is WhatsApp first, SMS as fallback: send the OTP on WhatsApp and, if it is not delivered within a few seconds or the number is not on WhatsApp, send it by SMS. Either way, an OTP has to be sent automatically by software connected to your login system — nobody types OTPs by hand.

When SMS is still the right choice

• Your customers are not all on WhatsApp — feature-phone users, older customers, rural audiences, or anyone with data switched off.
• Critical alerts that must reach everyone — bank debits, security warnings, delivery OTPs — where SMS is the fallback that always exists.
• Very short one-line notices where the extra richness of WhatsApp adds nothing.
• You have no opt-in yet. WhatsApp requires customers to agree to hear from you on WhatsApp; you may already hold SMS consent through DLT.

When WhatsApp is the better channel

• You want replies. A customer can answer an order update, ask about a product or reschedule an appointment in the same chat, and your team picks it up in a shared inbox.
• The message needs a picture, a document or a button — a brochure, an invoice PDF, a “Pay now” link.
• Regional languages. A Hindi message on WhatsApp costs the same as an English one; on SMS, Unicode shortens each part.
• You want to know it was read, not only delivered.
• Routine questions follow every message — a chatbot can answer them.

Using both, sensibly

Most Indian businesses that switch keep a small SMS setup running. A practical split: WhatsApp for offers, order and appointment updates, invoices and support conversations; SMS for customers who are not on WhatsApp and as the fallback for time-critical OTPs and alerts. Review the split every few months — as more customers opt in on WhatsApp, the SMS share usually shrinks on its own.