Why are my SNS SMS messages split when I receive them on my mobile Phone?

Short description

Amazon Simple Notification Service (Amazon SNS) lets you send messages with Short Message Service (SMS) texts. However, you might notice that a single message that's being sent is split into multiple messages.

Each SMS message can contain up to 140 bytes, and the character quota depends on the encoding scheme. For example, an SMS message can contain:

• 160 GSM characters
• 140 ASCII characters
• 70 UCS-2 characters

If the message exceeds the 140 bytes size quota, Amazon SNS sends it as multiple messages, each fitting within the size quota. In such instances, very long messages, or those with multi-byte characters, get split into several message parts. For more information, see Publishing to a mobile phone.

Resolution

When a message is split, each part of the split message contains additional information about the message part that precedes it. The recipient's device uses this information to display all the message parts in the correct order. Depending on the mobile carrier and device, multiple messages might be displayed as a single message. Or, messages can appear as a sequence of separate messages.

As a review of best practices, consider the following:

1. Turn on Amazon CloudWatch logs for your SMS Messages. The log field numberOfMessageParts specifies the number of message parts that the message contained.
   Note: You can also subscribe to the daily usage report from Amazon SNS to view the number of message parts sent.
2. Note that a split message is charged for each of its message part. The cost of split messages = number of message parts (n) x Destination country pricing per SMS message.
3. Send only the necessary characters. If your message contains characters that are outside the GSM 03.38 character set, that message can only have up to 70 characters per message part. A long message that contains more than 160 GSM 03.38 characters is split as well.
   Note: The character limitation of the SMS channel causes some senders to extensively abbreviate their messages. However, if you overuse abbreviations, some users might report your message as spam. Rewrite the message so that it's coherent without using an excessive number of abbreviations. For more information, see Limit the number of abbreviations that you use.
4. Use valid, safe links. Because of character limitation of SMS messages, very long URLs might get split across multiple messages. Use redirect domains to provide shortened URLs.
   Note: Don't use free link-shortening services such as tinyurl.com or bitly.com. This is because carriers tend to filter messages that include links on these domains. Instead, use paid link-shortening services that point to a domain that's dedicated exclusively to your company or organization. For more information about SMS character encoding, see SMS character limits in Amazon SNS.