SMS messages consist of text only. MMS messages may contain both text and multimedia content, such as images or GIFs.
SMS messages can contain either standard or non-standard characters and are organized into segments. SMS message rates are calculated based on the number of segments.
SMS messages which contain only standard characters may hold up to 160 characters per segment. For example, an SMS message that is 300 standard characters in total is considered two segments. Standard characters are defined using GSM-7 encoding and include letters, numerals, and most punctuation marks.
If an SMS message contains any non-standard characters (such as emojis, most non-English characters, or line breaks), it is defined using UCS-2 encoding. Messages with non-standard characters are broken into segments of 70 characters apiece. For example, an SMS message that’s 300 characters in length and contains at least one non-standard character would be counted as five segments.
MMS messages are not split into segments. Media files included in MMS messaging have a suggested size limit of 300 kB.