SMS character limits and how messages are ultimately delivered and displayed to patients can depend on a large number of factors including language and phone carrier. However, keeping messages close to the lower-end of the character limit will create a more consistent and reliable patient experience.

Character Limit of SMS Messages

Standard SMS messages have a 160 character limit. This limit is derived from how letters, symbols, and characters (including spaces) are encoded and transmitted. This encoding standard is referred to GSM-7. Staying below this limit ensures a higher rate of deliverability while preserving your intended formatting.

Character Limits of Translated Messages

Letters, symbols, and characters that are not natively part of the GSM-7 coding standard typically count as 2 characters instead of 1. So, for messages sent in languages other than English, it is common for the SMS message to have a character limit of 70. We have found that a message, sent as a single message in English, can appear as 2 or 3 messages when sent in Spanish. This is due to how our SMS Partner Twilio manages message encoding. Click here to learn more. 

What if an SMS Message is Over 160 Characters?

When an SMS message exceeds the 160 character limit, it will be sent as multiple individual messages, often referred to as concatenated messages. Each message in a concatenated series will have a max character limit of 153 per message. Important: Concatenated messages sent in languages other than English typically have a max character limit of 67 characters per message segment. 

Today, many carriers know to combine concatenated messages into a single message for the recipient. Major carriers including AT&T, T-Mobile/Sprint, and Verizon all support concatenated messages, though some smaller carriers may not. Instead, they will present the message in multiple segments, with some marking the numerical order of messages (1/3, 2/3, 3/3. etc) at the beginning of each text. Additionally, the type of cellular device can also impact whether or not the patient can receive a concatenated series as a single message.

Long Message Considerations

Message Failure

Concatenated messages have a character limit of 1,600. Messages over 1,600 characters will automatically fail to send. Note: The character limit failure is 700 for translated messages. 

Hyperlinks

Carriers may reject long messages containing hyperlinks. Artera automatically shortens any hyperlink over 25 characters to help prevent outright rejections. However, if the link is still rejected, patients might receive the text surrounding the link without the link itself. Alternatively, the link may be sent separately from the Fallback number, causing the link to appear in a separate message thread. Click here to learn more about the Fallback Process.