SMS Limits and Optimization
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Estimated reading time: 6 minutes
SMS is a fast and effective communication channel, but character limits and encoding impact delivery and cost. Understanding how these factors work can help businesses optimize their SMS campaigns and avoid unnecessary charges. With solutions like MyLINK SMS API, businesses can ensure compliance with SMS limits while maintaining cost efficiency.
Why Do SMS Messages Have a Character Limit?
The character limitations in SMS messages ensure the networks' efficient compatibility and transmission. Standard SMS uses 7-bit encoding, allowing up to 160 characters per message. However, if special characters or non-Latin languages are included, Unicode (UCS-2) encoding is used, which reduces the SMS limit to 70 characters per message.
What Is the Character Limit for an SMS?
The standard character limit for a single SMS depends on the encoding type:
GSM-7: Supports 160 characters per message.
UCS-2: Supports 70 characters per message.
If a message exceeds these SMS limits, it will be split into multiple SMS segments and sent as a concatenated message. Each segmented message includes additional metadata, reducing the available characters per segment:
GSM-7: 153 characters per segment
UCS-2: 67 characters per segment
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Understanding SMS Message Encoding
Message encoding is how human-readable formats are modified for transmission over cellular networks. There are two main types of SMS encoding:
7-bit encoding: Works best with English and other Latin-based languages.
Unicode encoding (UCS-2): Covers a wider range of characters, languages, and emojis. Unicode encoding counts for multiple characters in SMS messages, reducing the SMS limit.
For businesses looking to send longer messages or rich media content, RCS Messaging is an alternative worth considering.
How Many Characters Can a Sender ID Be?
The sender ID is the alphanumeric or numeric identifier that appears as the sender of an SMS. The allowed length varies depending on the country and carrier restrictions, but typically:
Alphanumeric sender IDs: Can be up to 11 characters (letters and numbers, but no spaces or special characters).
Numeric sender IDs: Usually range from 4 to 15 digits, depending on local regulations.
Short codes: These are shorter numeric sender IDs, typically 4 to 6 digits, used for marketing, notifications, and two-way messaging. Short codes may be shared or dedicated and often require registration before use.
Sender ID regulations vary from country to country. Some regions allow businesses to customize sender IDs freely, while others require registration or restrict sender ID usage to pre-approved formats. In some cases, sender IDs may be replaced with a generic numbers or an alphanumeric ID by local carriers due to compliance policies. Businesses using MyLINK SMS API can ensure that sender ID configurations align with regional SMS limits.
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Multipart SMS Messages and Cost Considerations
If an SMS message exceeds the character limits, it will automatically split into multiple parts. Due to reassembly, a data header must be added, further reducing the length of each segment:
GSM-7: 153 characters per segment
UCS-2: 67 characters per segment
While multipart messages enable longer texts, they also increase per-message costs since each segment is billed separately. LINK Mobility supports long SMS messages, but it is recommended to keep them within 10 message parts to maintain the best deliverability and user experience. Businesses can use the LINK Mobility SMS Length Calculator to optimize their message length and reduce unnecessary costs.
Best Practices for SMS Messaging
Keep Messages Clear and Concise
Ensure your text is easy to read and understand.
Be Mindful of Emoji Use
Emojis switch your message to Unicode encoding, reducing the character limit to 70 per SMS.
Segment Your Audience
Tailor messages for more relevant communication.
Include a Clear Call to Action
Encourage recipients to engage with a straightforward message.
Keep Your Message Short
Staying within 10 parts ensures better performance and cost efficiency.
Utilize the Character Count Wisely
Prioritize key information within the SMS limits for maximum impact.
Limitations for Customers Using an SMPP Integration
For businesses using SMPP (Short Message Peer-to-Peer Protocol) to send SMS messages, there are specific limitations to consider:
Encoding Restrictions: The SMPP gateway determines the encoding based on message content. If a message includes UCS-2 characters, all segments will be sent as UCS-2, increasing SMS limit usage.
Message Concatenation: SMPP supports concatenation, but each segment will be billed separately.
Sender ID Restrictions: Some networks may restrict sender ID usage or require pre-registration.
Short Code Limitations: Some markets may have restrictions on using short codes through SMPP, requiring businesses to apply for specific codes.
Throughput Limits: SMPP connections have defined throughput limits, meaning a high volume of messages may require additional connections to maintain performance while adhering to SMS limits.
Optimizing SMS Limits for Cost-Effective Messaging
Understanding SMS character limits and encoding is essential for efficient messaging. Choosing GSM-7 whenever possible can help reduce costs and keep messages within SMS limits. Businesses using SMPP integrations should be aware of sender ID and throughput limitations. By optimizing message content and leveraging tools like MyLINK SMS API and the LINK Mobility SMS Length Calculator, companies can ensure reliable and cost-effective SMS communication while staying within SMS limits.
Ready to optimize your SMS messaging?
Discover how MyLINK SMS API can help you reduce costs, ensure compliance, and deliver efficient, high-performing SMS campaigns. Get started today!
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