OTP by WhatsApp or by SMS: which is better for verifying users
· 3 min read
Every serious sign-up ends the same way: “enter the code we have sent you”. The question is which way to send it. WhatsApp launched the authentication category for exactly this — specific templates with a copy-code button — and it deserves an honest comparison with SMS.
What each channel offers
WhatsApp authentication: Meta's standard template (the text cannot be customised, and that is on purpose: it prevents phishing with disguised templates), a “copy code” button, delivery with read confirmation. Meta bills the conversation separately, and our platform charges its flat rate per message.
SMS: it reaches any mobile phone, whether or not it has WhatsApp, without depending on the app being installed or on a third-party platform's policy. In Spain the receipt confirms delivery to the handset. It is the channel banks still use for a reason.
The failures nobody tells you about
- A user without WhatsApp (or with a recently changed number) receives nothing: you need to detect the failure and retry through another channel, quickly.
- In some countries the SMS receipt only confirms that the network accepted it, not that it reached the phone — we have it measured by destination and we warn you before sending.
- SMS pumping (inflating verifications towards expensive ranges) is fought with limits per IP and per destination: our verification API has them built in.
Our recommendation: both, with a fallback
The verification API generates the code, controls expiry and retries, and never stores the code in plain text — neither in the database nor in the dashboard history: only its fingerprint. You can send the OTP by WhatsApp and, if it is not recorded as delivered within a few seconds, resend it by SMS. The user sees only one thing: the code arrives.
A wrong code is answered with the status invalid, not with an HTTP error:
your application tells “they made a mistake” apart from “something broke”,
which in a sign-up form is the difference between retrying and losing the
user.
API documentation · Prices by channel · Test mode at no cost when you create your account.
Fine-tuning the decision by type of business
Banking and fintech: SMS is still the reference channel for the second factor — it reaches any handset, without an intermediate app, and the regulator knows it. WhatsApp authentication works well as an option the user chooses, not as an imposition.
Marketplaces and consumer apps: WhatsApp's copy-code button reduces friction at sign-up, and your young audience probably lives there. The SMS retry, triggered from your code, covers everyone else.
B2B and business software: the corporate phone does not always have WhatsApp; SMS is the option without surprises.
International: the cost of SMS varies by country — the rate per destination is published — and so does the reliability of the receipt. WhatsApp costs the same everywhere, but it requires the number to have an active account. The right combination usually comes from looking at your real map of users, not from a general rule.