How does SMS character encoding affect the 160-character limit?

The Standard 160 Character Limit

In traditional SMS (Short Message Service) encoding, each character counts toward your message limit. The default character encoding system used is GSM-7. This encoding can handle 160 characters, and these characters include:

• Standard alphabetic characters (A-Z, a-z)
• Numbers (0-9)
• Basic punctuation (e.g., !, ?, ., etc.)

Each character from this set takes up just 1 byte of memory, which is why you're allowed to send up to 160 characters in a single message.

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What Happens When You Add Emojis?

Emojis, however, use a different encoding system called UCS-2 (Universal Character Set 2). UCS-2 is capable of encoding a much wider range of characters, including the diverse set of emojis we use today. But here's the catch: UCS-2 characters are more memory-heavy. Each emoji or special character requires 2 bytes of memory instead of just 1.

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Impact of Emojis on Character Limit

Because emojis use more memory, adding even a single emoji reduces the total number of characters you can send in one SMS. In fact, with UCS-2 encoding, the limit drops from 160 characters to 70 characters per message. This is why if you add an emoji or any non-GSM-7 character (like accented letters, certain symbols, or non-Latin scripts), your message will be shortened in terms of character count.

Example:

• SMS with only text: "Hello, how are you doing today?" (31 characters)
• SMS with an emoji: "Hello, how are you doing today? 😊" (30 characters, with the emoji taking up 2 bytes)

In this case, the emoji reduced the total number of characters by 1. However, if you were to send a longer message with multiple emojis, you could easily hit the 70-character limit.

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What Happens When You Exceed 160 Characters?

If your message exceeds the 160-character limit, the SMS will automatically be split into multiple segments. Each segment will include a header with metadata about the message to help your phone reassemble them correctly. Keep in mind that:

• Each segment is usually 153 characters long when using GSM-7 encoding (due to the need for this extra header).
• With UCS-2 encoding, each message part will be limited to 67 or 68 characters.

So, even a message with an emoji can quickly become segmented if it's too long.

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Key Takeaways:

• Standard text messages use GSM-7 encoding, allowing 160 characters per SMS.
• Emojis and special characters use UCS-2 encoding, reducing the limit to about 70 characters per SMS.
• When your message exceeds the character limit, it is split into multiple SMS parts, which may impact formatting.

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Best Practices for SMS Communication:

• Keep your SMS messages concise to avoid exceeding character limits.
• If you want to use emojis, be mindful that they reduce the number of characters you can send.
• Consider segmenting your messages carefully to ensure they remain readable when split.

By understanding how character encoding works in SMS, you can avoid potential issues and communicate more efficiently.