OTP
One-time passwords over SMS or WhatsApp, verified in one call.
- Codes hashed at rest, expiring on a timer
- Rate limits per mobile, purpose and IP
- SMS fallback when WhatsApp fails
- Fixed code 123456 with test keys
Channels
Every way to reach a phone, behind one API
OTP, SMS, WhatsApp and replies share one set of keys, statuses, webhooks and one prepaid wallet. Pick the channel per message — or let OTP fall back from one to another.
Transactional SMS
DLT-compliant SMS with approved templates and sender IDs.
- Template and header checked before sending
- Automatic GSM-7 / Unicode encoding and parts
- Idempotency keys so retries never double-send
- Failover across providers
v2
Simple SMS API
number, message, header and DLT template ID — the fields every Indian gateway uses.
- JSON or a plain form post, key in header or body
- Up to 100 numbers per request
- The final text is matched to your DLT template
- Cost and balance in every response
Bulk campaigns
Thousands of personalised messages from a list or CSV.
- Schedule ahead, follow progress, stop mid-flight
- Contact lists with custom columns
- Opt-outs skipped automatically
- Charged per message as it is queued
WhatsApp Business
Template and session messages on the official Cloud API, through SMS21’s account.
- Utility, marketing and authentication templates
- Replies within the 24-hour window
- Same statuses and webhooks as SMS
- WhatsApp OTP with SMS fallback
Plugin
WhatsApp Official
Connect your own Meta WhatsApp Business Account and send from your verified number.
- Your templates synced from Meta, or created in SMS21
- Images, videos and documents
- Campaigns and a reply inbox
- Same /v1/whatsapp API
Plugin
WhatsApp Connect
Link a WhatsApp number by scanning a QR code and send from it.
- Several numbers, rotating automatically
- Personalised campaigns and media
- Per-device pacing and daily limits
- Dashboard and API
Inbound & opt-outs
Receive replies and keep a suppression list every sending API respects.
- Replies forwarded to your webhooks
- STOP and START handled automatically
- Suppression list managed per company
- Test replies before a number is live
Delivery status
One set of statuses across every provider.
- Per message, in reports or by webhook
- Signed webhooks, retried and replayable
- Provider response kept for support
- Refunds when delivery fails, if your rate says so
Three ways to send on WhatsApp
Use SMS21’s account to start immediately, connect your own Meta account for your brand and number, or link a phone by QR code for conversational sending.
| Feature | WhatsApp Business | WhatsApp Official | WhatsApp Connect |
|---|---|---|---|
| Sends from | SMS21’s WhatsApp account | Your own verified number | Your linked WhatsApp number |
| Meta setup needed | Your Meta Business account | ||
| Official Cloud API | |||
| Approved templates | |||
| Free text any time | |||
| Media (image, video, document) | |||
| Campaigns from the dashboard | |||
| Replies inbox | |||
| Risk of number restrictions | Low | Low | Higher — unofficial protocol |
Start today
Build against the sandbox, go live when you are ready
Create an account and a test key in minutes. Nothing is delivered and nothing is charged until you switch to a live key.