Deliverability and read rate comparison
SMS has the highest delivery rate: close to 98-99% on any phone type, including non-smartphones. WhatsApp has a 95-97% delivery rate but only on smartphones with WhatsApp installed.
For messages requiring action (link clicks, replies, confirmations), WhatsApp significantly outperforms SMS. For simple informational messages where reading is sufficient, the difference is smaller.
Cost comparison
For simple one-way communications (OTP, critical alerts), SMS can be cheaper than WhatsApp, especially at low volumes. For bidirectional or rich content communications, WhatsApp offers superior value per conversation that justifies the cost.
When SMS is the right choice
SMS remains the preferred channel for: OTP and verification codes (maximum compatibility and speed), urgent mission-critical messages, communications to elderly users who do not use WhatsApp, and markets with low smartphone penetration.
Optimal omnichannel strategy
The optimal strategy for most businesses: attempt WhatsApp first for main communications, if the number is not on WhatsApp or the WhatsApp message is not delivered within X minutes, send an SMS as fallback. Chat API supports this fallback logic natively.
