Concatenated SMS messages are long SMS messages that are split into multiple smaller SMS parts and then joined back together on the recipient’s mobile phone. This allows businesses to send longer text messages when the content exceeds the normal character limit of a single SMS.
At BulkSMSOnline.com, concatenated SMS messages are useful for sending longer customer alerts, appointment reminders, delivery updates, payment notifications, OTP instructions, marketing messages, and other business SMS communication that cannot fit into one standard SMS part.
How Does a Concatenated SMS Work?
A normal SMS has a limited number of characters. When your message becomes longer than the single-part limit, the SMS is divided into multiple segments. These segments are sent through the SMS network in sequence. Once they reach the recipient’s phone, the device usually combines them and displays the full message as one complete SMS.
For example, if you send a long English message that requires three SMS parts, the customer will usually see one full message on their phone. However, your account will be charged for three SMS parts because the network processed the message as three separate SMS segments.
Concatenated SMS Character Limits
The number of characters available in each SMS depends on the message encoding. English messages usually use GSM-7 encoding, while messages containing Arabic, Chinese, emojis, special symbols, or unsupported characters usually use Unicode encoding.
| SMS Type | Single SMS Limit | Concatenated SMS Limit Per Part | Example Usage |
|---|---|---|---|
| GSM / English SMS | Up to 160 characters | Around 153 characters per part | English marketing messages, reminders, alerts, and notifications |
| Unicode SMS | Up to 70 characters | Around 67 characters per part | Arabic, Chinese, emojis, special symbols, and non-GSM text |
Why Does a Concatenated SMS Have Fewer Characters Per Part?
When an SMS is split into multiple parts, a small amount of space is used by technical information that tells the phone how to join the parts together. This is why a single English SMS can hold up to 160 characters, but a concatenated English SMS usually allows around 153 characters per part.
The same applies to Unicode SMS. A single Unicode SMS can hold up to 70 characters, but a concatenated Unicode SMS usually allows around 67 characters per part.
Will the Customer See One Message or Many Messages?
In most cases, the customer will see the concatenated SMS as one complete message. The mobile device automatically joins the parts together and displays the full text in the correct order.
However, display behavior can depend on the recipient’s device, mobile operator, destination country, route type, and network support. Some older phones or certain networks may display long messages differently, so it is always recommended to test your message before sending a large campaign.
How Are Concatenated SMS Messages Charged?
Concatenated SMS messages are charged according to the number of SMS parts used. Even if the recipient sees one complete message, the SMS gateway and mobile network still process each part separately.
For example:
- If your message fits into one SMS part, it is charged as 1 SMS.
- If your message requires two SMS parts, it is charged as 2 SMS parts.
- If your message requires three SMS parts, it is charged as 3 SMS parts.
- If your message contains Unicode characters, it may use more parts than expected.
Before sending a large campaign, always check the message length, encoding type, destination country, and selected route to estimate the total SMS cost correctly.
You can review current country and route pricing on the Bulk SMS Pricing page.
What Makes an SMS Change From GSM to Unicode?
A message may switch from GSM to Unicode when it includes characters that are not supported by the standard GSM character set. This can reduce the number of characters allowed per SMS part and increase the number of SMS credits used.
Common examples include:
- Arabic, Chinese, Russian, or other non-Latin text
- Emojis
- Curly quotation marks copied from documents
- Special currency symbols
- Unusual punctuation or hidden formatting
- Accented characters that are not supported by GSM-7
If your campaign cost looks higher than expected, check whether your message has changed to Unicode because of special characters.
When Should You Use Concatenated SMS?
Concatenated SMS is useful when your business needs to send more detailed information than a short SMS can contain. Common use cases include:
- Appointment reminders with full instructions
- Delivery and logistics updates
- Payment reminders and account notices
- Event details and confirmations
- OTP messages with security instructions
- Customer service updates
- Marketing messages with important terms
- Emergency or operational alerts
For general promotional campaigns, shorter messages are usually better because they are easier to read, cost less, and may perform better with customers.
Best Practices for Concatenated SMS Messages
To improve customer experience and control SMS costs, follow these best practices before sending long SMS messages:
- Keep the message as short and clear as possible.
- Use GSM English characters when possible to allow more characters per part.
- Avoid emojis and unnecessary special symbols if they are not required.
- Check the message parts before sending a large campaign.
- Test the SMS on different phones and operators in the target country.
- Use trusted links and avoid suspicious URL shorteners.
- Follow destination country rules for sender ID, content, and marketing SMS.
- Choose the right route depending on whether the message is promotional, transactional, or time-sensitive.
Does the SMS Route Affect Concatenated SMS Delivery?
Yes, the selected SMS route can affect delivery speed, sender ID behavior, delivery report visibility, and overall campaign reliability. Long SMS messages may also be affected by destination network rules and route handling.
If you are sending important messages such as OTP instructions, payment alerts, account notifications, or customer service updates, it is recommended to choose a suitable route and test delivery before sending to a large audience.
You can learn more about route options on the SMS Routing page.
Can I Send Concatenated SMS Through the API?
Yes. Businesses and developers can send long SMS messages through the BulkSMSOnline API. When sending concatenated SMS by API, make sure your application checks the message length, encoding type, destination country, selected route, and expected SMS parts before submitting the request.
It is also important to encode your request correctly and review the API response after sending. For delivery tracking, you can use delivery report callbacks or webhooks where supported.
For technical integration details, visit the BulkSMSOnline Developers page.
Country and Network Restrictions
Concatenated SMS delivery may vary by country and mobile operator. Some destinations may have specific rules for sender ID, marketing content, links, Unicode messages, OTP messages, and long SMS handling.
Before sending a large campaign, review destination-specific requirements and test your SMS with a small group of numbers first.
You can browse country-specific information through the Bulk SMS Countries section.
Need Help With Concatenated SMS?
If you are not sure why your message is being split into multiple parts, why it changed to Unicode, or why the customer did not receive the full message correctly, BulkSMSOnline support can help review the issue.
When contacting support, please provide the message text, destination country, recipient number, sender ID, selected route, sending time, message ID, and delivery report status.
You can visit the BulkSMSOnline Help Center or contact our team through the Contact Us page.
Frequently Asked Questions
What is a concatenated SMS message?
A concatenated SMS message is a long SMS that is split into multiple smaller parts and then reassembled on the recipient’s phone as one complete message where supported.
Why is my SMS split into multiple parts?
Your SMS is split into multiple parts when it exceeds the character limit of one SMS. English GSM messages usually allow up to 160 characters for one part, while Unicode messages usually allow up to 70 characters for one part.
Why does a long SMS have 153 characters per part instead of 160?
Concatenated SMS uses a small amount of space in each part for technical joining information. Because of this, long English SMS messages usually allow around 153 characters per part.
Are concatenated SMS messages charged as one SMS?
No. Concatenated SMS messages are charged based on the number of SMS parts used, even if the customer sees the message as one full SMS.
Can emojis make my SMS more expensive?
Yes. Emojis can change the SMS from GSM encoding to Unicode encoding, which reduces the character limit per part and may increase the number of SMS parts used.
Will all phones display concatenated SMS correctly?
Most modern phones display concatenated SMS as one complete message, but behavior may vary depending on the device, mobile operator, destination country, and network support.
Can I send concatenated SMS through BulkSMSOnline API?
Yes. BulkSMSOnline supports SMS sending through API, and developers can send long messages as long as they check message length, encoding, route, country rules, and expected SMS parts before sending.