Send SMS via API,
and why WhatsApp often does it better.
SMS is still the most universal channel - but it caps at 160 characters per segment, accepts no media, offers no read receipts and bills every segment. Here's what sending SMS via API really forces on you, and how our REST API sends rich WhatsApp messages from your normal account.
The context
How do you send an SMS via API, and where's the limit?
Sending an SMS via API means calling an endpoint like Twilio's with a number and a text; the message then goes out over the A2P (application-to-person) network, with all the constraints inherited from legacy SMS.
Technically, sending SMS via API is simple: a POST with a recipient, a sender and a text body. But SMS carries a technical legacy from the 1990s. Each message is split into 160-character segments (only 70 if you use accents or emojis in Unicode encoding), and each segment is billed separately - a slightly long message can cost triple a short SMS.
SMS carries no media: no image, no PDF, no button. It returns no read receipt - at best a carrier delivery receipt, which doesn't tell you whether the recipient saw the message. Internationally, prices vary widely from one country to another, and deliverability depends on carrier filtering, local A2P rules and sender reputation.
For many business use cases - OTP, notifications, reminders, follow-ups, support - these limits weigh heavily. That's exactly where sending WhatsApp messages via API becomes a better channel: rich messages, delivered and read receipts, flat price and unlimited. That's what Unlimited Messaging offers.
Comparison
Sending SMS via API vs sending WhatsApp via API
The same goal - reaching a recipient with a message from your code - but two channels with very different constraints. Here, line by line, is what A2P SMS forces on you and what our WhatsApp API adds on top.
| SMS (carrier / A2P API)per billed segment | Unlimited Messaging (WhatsApp)your account, via API | |
|---|---|---|
| Length / format | 160 chars/segment (70 in Unicode) | Long messages, free text |
| Media | Text only, no attachments | Images, PDF, videos via URL |
| Read receipts | Carrier delivery only | Delivered and read receipts |
| Cost | Per segment, multiplied if long | Flat monthly price, unlimited |
| Deliverability | Carrier filtering, A2P rules | Application channel, tracked status |
| International | Highly variable rates per country | 180+ countries, same subscription |
| API / webhooks | REST endpoint + webhooks | REST endpoint + webhooks |
| Unlimited | No, pay-per-use billing | Yes, unlimited messages |
Our approach
The sending API without the SMS limits
We keep the simplicity of API sending - REST, webhooks, Python and TypeScript SDKs - and remove the SMS caps: length, media, receipts, per-segment cost.
Rich messages, no cap
Forget the 160 characters and segment splitting. Send long text, images, PDFs and videos via API, with no hidden surcharge per segment.
Real read receipts
Where SMS stops at carrier delivery, you get delivered and read webhooks: you know whether your OTP or notification was actually seen.
Unlimited, flat price
No per-segment cost, no rate that explodes internationally. A clear monthly subscription, unlimited WhatsApp messages to 180+ countries.
Ready in minutes
Create your API key, make a POST, you're off. No A2P number to provision, no sender validation to wait for.
- Max characters per SMS segment
- 160Max characters per SMS segment
- Per-segment cost with us
- 0Per-segment cost with us
- Countries covered, same subscription
- 180+Countries covered, same subscription
- From key to first message
- 5 minFrom key to first message
How it works
Replace sending SMS via API in three steps
- 1
Link your account
Connect your existing WhatsApp account to Unlimited Messaging by scanning a QR code, like WhatsApp Web. No A2P number to buy.
- 2
Get your API key
Generate a token from the dashboard. Create as many as you have projects, revocable at any time.
- 3
Call the REST API
A POST /messages with the recipient and the text, just like an SMS API. We route the WhatsApp message and you get the delivered and read webhooks.
FAQ
Questions about sending SMS via API
Sources
Sources & references
To check the information in this article for yourself:
Written by
Ilian · Senior Software Engineer
A senior software engineer, he founds and runs several tech companies. He builds products around messaging APIs, automation and AI integration, and shares here what he learns while building.
Move from SMS via API to a better channel.
Link your account, generate your API key, send your first WhatsApp message today.
Get my API key