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Concatenated SMS (C-SMS) —
Long-form International
Text Messaging

Send business messages longer than the 160-character SMS limit, delivered reliably across 200+ countries with automatic segmentation and reassembly.

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612
ASCII chars
268
Unicode chars
200+
Countries
800+
Carriers

What is Long SMS (Concatenated SMS)?

Long SMS (Concatenated SMS or C-SMS) is a messaging technology that enables businesses to send text messages exceeding the standard 160-character SMS limit. When a message is longer than a single SMS, it is automatically divided into multiple SMS segments and reassembled into a single, readable message on the recipient’s mobile device.

Long SMS is widely used for business communications that require more detailed information while maintaining the broad compatibility and reliability of SMS. Common use cases include OTP and authentication, banking and financial notifications, appointment reminders, delivery and logistics updates, customer service notifications, marketing campaigns, and government announcements.

How it works
1. Message
created
2. Automatically
segmented
3. Reassembled
on device
One long message, delivered
as a seamless experience.
Key benefits:
Send messages longer than the standard SMS character limit
Automatic segmentation and seamless reassembly on supported devices
Compatible with most mobile networks and handsets worldwide
Ideal for enterprise notifications and customer communications
Easily integrated through SMS APIs and enterprise messaging platforms

What is Long SMS?

Long SMS (Concatenated SMS or C-SMS) allows businesses to send messages longer than the standard 160-character SMS limit. When a message exceeds the limit, it is automatically divided into multiple SMS segments and reassembled on the recipient’s phone.

OTP
Banking notifications
Appointment reminders
Customer support
Marketing campaigns

SMS vs Long SMS vs MMS

FeatureSMSLong SMSMMS
Characters160Unlimited (segmented)2,000
ImagesNoNoYes
InternationalYesYesLimited

Character limits

EncodingSingle SMSMulti-part SMS
GSM160153
작Unicode7067

Long SMS vs LMS

Long SMS is an international standard; LMS is a Korea-specific long message type.

FeatureLong SMSLMS
StructureSplit into SMS segmentsOne long message
ProtocolStandard SMS protocolLMS protocol
CoverageInternational supportMostly domestic
DeviceWorks on basic phonesDepends on network

Use cases by industry

Long SMS communicates what matters, when it matters.

Banking
Transaction alerts,
fraud alerts,
monthly statements.
Healthcare
Appointment reminders,
prescription
notifications.
Retail
Coupons, promotions,
order updates.
Logistics
Delivery notifications,
driver arrival,
tracking.
Government
Emergency alerts,
citizen
notifications.

Message example

1{
2 "type": "CSMS",
3 "from": "SureM",
4 "to": ["+819012345678"],
5 "message": "Your shipment (#KR-20260701-4829) is delayed due to customs clearance at Incheon port."
6 Expected release: July 5. For inquiries, contact 1588-0000.
7}

Operational note

Messages exceeding 4 concatenated segments (612 ASCII / 268 Unicode characters) face higher delivery risk on some international carriers, as certain networks impose per-message size limits at the carrier level.

For content exceeding these limits, SureM recommends splitting into separate messages or switching to MMS or WhatsApp Business for image-rich or document-heavy content.

Why choose SureM?

26 yrs
messaging experience
1,800+
enterprise customers
200+
countries
800+
carrier connections
Direct Korea
carrier connectivity
SMPP/API
integration
High-volume
messaging infrastructure

Frequently asked questions

What is C-SMS and how is it different from standard SMS?
C-SMS (Concatenated SMS) automatically splits messages exceeding the standard 160-character (ASCII) or 70-character (Unicode) SMS limit into multiple segments, which are reassembled into a single message on the recipient’s handset. Unlike standard SMS, C-SMS allows up to 612 ASCII or 268 Unicode characters in a single logical message.
How is C-SMS charged?
C-SMS is billed per SMS segment. A message that spans three segments is charged as three SMS. Segment counts follow the concatenation limits: 153 ASCII or 67 Unicode characters per segment once a message becomes multi-part.
Can C-SMS deliver Korean, Chinese, or Japanese characters?
Yes. Non-Latin scripts are sent using Unicode (UCS-2) encoding, which supports Korean, Chinese, Japanese, Arabic, and other character sets. Unicode messages use 70 characters per single SMS and 67 per segment when concatenated.
Is there a maximum length for C-SMS?
In practice, most carriers reliably deliver up to 4 concatenated segments (612 ASCII / 268 Unicode characters). Longer messages may be truncated or rejected by some international carriers that impose per-message size limits.
Which countries support C-SMS delivery?
C-SMS is supported across 200+ countries through SureM’s 800+ carrier connections. Reassembly is handled on the recipient’s device, so no special handset configuration is required.
Is Long SMS more expensive than SMS?
Long SMS costs more than a single SMS only because it consumes multiple segments. Each segment is priced as one SMS. For the same content, C-SMS is typically far more cost-effective than MMS.
When should businesses use C-SMS?
Use C-SMS whenever a message exceeds the single-SMS limit but doesn’t require images — OTP with context, detailed notifications, banking alerts, appointment reminders, and delivery updates are common examples.
Is C-SMS supported internationally?
Yes. C-SMS is supported across 200+ countries through 800+ carrier connections, with reassembly handled on the recipient’s device.
Can APIs send Long SMS?
Yes. Long SMS is sent through the same REST API or SMPP integration as standard SMS; segmentation and reassembly are handled automatically.
Related
SMS APIInternational SMSSMPPMMSDelivery ReceiptVoice OTP

Need help choosing between
SMS, Long SMS, MMS, or RCS?

Talk with a SureM messaging specialist.

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