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    Short Message Service:Message sending rules

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    Short Message Service:Message sending rules

    Last Updated:Jun 03, 2026

    Learn how SMS encoding, segmentation, and sending limits affect cost and delivery.

    Costs and segmentation

    SMS cost depends on encoding, content length, and segment count.

    Billing

    • Billing unit: Charged per segment, not per send request.

    • Formula: Total cost = Unit price × Segment count.

    • Cost factors:

      • Encoding: UCS-2 holds fewer characters per segment than GSM-7, producing more segments.

      • Length: Longer content requires more segments.

      • Signatures and variables: Signature characters and variable values affect encoding and billable length.

    Calculate segment count and length

    The system selects encoding based on message content. Each encoding has different segmentation thresholds that affect segment count and cost.

    Important

    If a message contains any non-GSM-7 character, such as a Chinese punctuation mark (，) or an emoji ( image), the entire message is switched from GSM-7 to UCS-2 encoding, which increases the number of segments and the cost.

    Message type

    Character counting

    Message segmentation

    English-only messages

    (GSM-7 encoding)

    Standard characters (letters, digits, and common symbols): each counts as one character.

    Extended characters (| ^ € { } [ ] ~ \): each counts as two characters.

    For more information about GSM-7 characters, see GSM-7 characters.

    Note

    If a message contains any character not in the GSM-7 standard or extended set, the entire message is billed under UCS-2 rules.

    Single messages can contain up to 160 characters. Longer messages split into 153-character segments, each billed separately.

    Example: A 350-character message will be split into three segments (153 + 153 + 44) and billed as 3 messages.

    Messages in other languages

    (UCS-2 encoding)

    Every character (Chinese characters, letters, symbols, spaces) counts as 1 character.

    Single messages can contain up to 70 characters. Longer messages split into 67-character segments, each billed separately.

    Example: A 150-character message will be split into three segments (67 + 67 + 16) and billed as 3 messages.

    Check characters before sending

    • Review content before sending to avoid unintended encoding switches, especially for GSM-7 messages.

      • Non-standard characters: Any non-GSM-7 character (Chinese punctuation, full-width symbols, emojis) switches the entire message to UCS-2, increasing segment count.

      • Variable values: Verify that resolved variable values contain no non-GSM-7 characters. Encoding is determined by the complete message, including resolved variables.

    • SMS signatures count toward total message length and affect encoding.

    • Use the content preview tool in the Alibaba Cloud SMS console to verify encoding and segmentation.

      Note

      The content preview tool is available at:

      Go Globe > SMS Campaign > Create Campaign

      Go China > Templates > Create Template

      Go China > Broadcast > Create Campaign

    image.png

    A GSM-7 message of 160 characters or fewer is billed as one segment.

    image.png

    A GSM-7 message exceeding 160 characters splits into 153-character segments. This example splits into two segments (153 + 8 characters).

    image.png

    A stray Chinese comma forces UCS-2 encoding.
    This example splits into three segments (67 + 67 + 25 characters).

    Message sending limit

    To prevent spam and maintain channel stability, the default limit is 20 messages per mobile number per day.

    To configure a custom sending limit, see Configure messaging limit.

    GSM-7 characters

    The GSM-7 character set includes a standard set and an extended set.

    Standard GSM-7 characters, each counting as one character:

    GSM-7 standard characters

    A

    B

    C

    D

    E

    F

    G

    H

    I

    J

    K

    L

    M

    N

    O

    P

    Q

    R

    S

    T

    U

    V

    W

    X

    Y

    Z

    a

    b

    c

    d

    e

    f

    g

    h

    i

    j

    k

    l

    m

    n

    o

    p

    q

    r

    s

    t

    u

    v

    w

    x

    y

    z

    à

    Å

    å

    Ä

    ä

    Ç

    É

    é

    è

    ì

    Ñ

    ñ

    ò

    Ø

    ø

    Ö

    ö

    ù

    Ü

    ü

    Æ

    æ

    ß

    0

    1

    2

    3

    4

    5

    6

    7

    8

    9

    &

    *

    @

    :

    ,

    ¤

    $

    =

    !

    >

    #

    -

    ¡

    ¿

    (

    <

    %

    .

    +

    £

    ?

    "

    )

    §

    ;

    '

    /

    _

    ¥

    Δ

    Φ

    Γ

    Λ

    Ω

    Π

    Ψ

    Σ

    Θ

    Ξ

    Extended GSM-7 characters each count as two characters due to a required escape character:

    ^

    {

    }

    \

    [

    ]

    ~

    |

    €

    The GSM-7 set also includes these non-printing characters, each counting as one character:

    • Space

    • Line feed: Ends a line of text.

    • Carriage return: Returns the cursor to the start of a line.

    • Escape: Automatically added before each extended character.