The Twilio SMS character limit is 160 characters for a single message in GSM-7 encoding, or 70 if any character forces UCS-2 encoding, such as an emoji or a curly quote. Longer messages split into segments of 153 (GSM-7) or 67 (UCS-2) characters. Twilio supports long messages up to 1,600 characters across Programmable Messaging channels.
The number most people know is 160. The number that surprises them is 70. Which one applies to your message depends on a single question: does every character fit in the GSM-7 alphabet? One emoji or one curly quote, and the answer's no.
Why the limit is 160, and when it drops to 70
Twilio's docs trace the 160 back to the GSM 03.38 recommendation, which limited a single SMS to 140 bytes. That's 160 characters in 7-bit encoding. GSM-7 covers 128 different characters, and it isn't the same as ASCII, so some characters you'd expect to be safe aren't.
If a message includes a UCS-2 character, such as an emoji or a Chinese hanzi, SMS switches to UCS-2 encoding for the whole message. That lowers the single-message limit from 160 to 70 characters. A curly or smart quotation mark is a UCS-2 character too, which is how a message pasted from a word processor can quietly lose more than half its room.
Every SMS length limit Twilio lists
| Item | Limit | Applies to |
|---|---|---|
| Single SMS | 160 characters | GSM-7 encoding |
| Single SMS | 70 characters | UCS-2 encoding (emoji, non-Latin scripts, curly quotes) |
| Segment size in a long message | 153 characters | GSM-7 |
| Segment size in a long message | 67 characters | UCS-2 |
| Segment size, toll-free to US or Canada | 152 / 66 characters | GSM-7 / UCS-2 |
| Long message maximum | 1,600 characters | Twilio Programmable Messaging, including SMS |
| Recommended length | Under 320 characters | Twilio guidance for deliverability |
What happens past one message
Longer SMS messages are split into segments that are reassembled on the recipient's device. Each segment carries 153 characters of data plus seven characters of header metadata, which is why the per-segment number is lower than 160. In UCS-2, messages over 70 characters split into segments of 67 characters each.
Twilio's own example makes it concrete: a 161-character GSM-7 message is sent as two segments, one with 153 characters and one with eight. Toll-free multi-segment SMS to the US or Canada have slightly smaller segments, 152 for GSM-7 and 66 for UCS-2. Those toll-free numbers apply to the US and Canada only.
One curly quote can double your segments
Twilio Docs, in How long can a message be?, flag the trap. One curly quote or emoji changes the whole message to UCS-2 and cuts the single-message limit from 160 to 70, so a message that looked like one segment can become two or three. A 150-character reminder fits in one GSM-7 segment; add a single emoji and the same text needs three UCS-2 segments of up to 67 characters.
Keeping messages in GSM-7
- Type messages in a plain text editor, or check for curly quotes and apostrophes before you send.
- Use Twilio's Message Segment Calculator, which shows encoding, segment count and character limits before you send.
- Switch on Twilio Smart Encoding, which replaces certain non-GSM characters with GSM equivalents, such as straight quotation marks for curly ones.
- Keep messages under 320 characters, which Twilio recommends for deliverability and user experience.
- Leave emojis out of reminders and alerts, where clarity matters more than decoration.
If you need emojis or non-English characters, RCS uses UTF-8 encoding, which supports them natively, and Twilio says it sends messages up to 1,600 characters without segmentation.
Other SMS providers use the same rules
Vonage says the maximum length of a single SMS is 140 bytes, equal to 160 GSM 7-bit characters or 70 UCS-2 characters, and that longer messages are split into parts. The limits come from the SMS standard, not from one provider. My Twilio alternatives roundup covers other providers, and my SMS marketing guide for small businesses covers what to say once you're inside the limit.
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My advice for SMS that stays in one piece
Write to 160 characters, plain text only, and run anything important through the Message Segment Calculator before it goes out. Turn on Smart Encoding so stray curly quotes don't push you into UCS-2. If a message needs more room, keep it under 320 characters, and save emojis for channels that handle them, such as RCS.
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Frequently asked questions
What is the Twilio SMS character limit?
160 characters for a single GSM-7 message and 70 for UCS-2. Twilio supports long messages up to 1,600 characters.
Why does my message split into more segments than expected?
A non-GSM character such as an emoji or a curly quote switches the message to UCS-2, which lowers the limit to 70 for one message and 67 per segment after that.
How many characters are in each segment of a long message?
153 for GSM-7 and 67 for UCS-2, because seven characters of each part go on segmentation metadata.
What does Smart Encoding do?
It replaces certain non-GSM characters with GSM equivalents, such as curly quotes with straight quotes, so messages can stay in GSM-7.
What length does Twilio recommend?
Under 320 characters, for deliverability and user experience.
