Overview WhatsApp is one channel in Twilio's Messaging platform. All channels share the same API — see for the full channel comparison and onboarding sequence. Twilio routes WhatsApp through the Programmable Messaging API — all numbers use prefix. Two sending modes apply: free-form (within 24 hrs of last inbound) and template (anytime). Sending free-form outside the window causes silent delivery failure — always check which mode is required. | Mode | When allowed | Parameters | |------|-------------|------------| | Free-form | Within 24 hrs of last inbound from user | , optional | | Template…