Why do I see question marks in my SMS message instead of the original characters?


Why do I receive question marks in my SMS message instead of original characters?

Applies To

  • SMS Messages
  • Non-Latin Alphabet


This can occur in languages using a non-Latin alphabet. This happens when using characters in a message that are not part of the generic GSM7 character set. To successfully send these characters you will need to use Unicode encoding.

To specify Unicode encoding for your message add this parameter to your GET or POST API URL:


Note that type is an optional parameter. This can be omitted for text (default), but is required when sending a Binary (binary), WAP Push (wappush), Unicode message (unicode), vcal (vcal) or vcard (card).

Parameters that Vonage allows you to use to encode your messages are detailed here. The basic generic GSM7 character set is defined here. This encoding only applies to the message body, not the Sender ID. All Sender IDs are Latin alphabet alphanumeric only.

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