Unicode SMS

Unicode SMS allows you to send messages in non-Latin scripts including Hindi, Tamil, Telugu, Bengali, Marathi, and other regional Indian languages. This guide covers encoding types, character limits, and how to send Unicode messages through Exotel.

What Is Unicode SMS?

Standard SMS uses GSM-7 encoding, which supports 160 characters from the basic Latin alphabet, digits, and common symbols. Unicode (UCS-2) encoding supports characters from virtually all languages and scripts, but reduces the character limit per segment.

Encoding	Characters Supported	Single SMS Limit	Concatenated Segment Limit
GSM-7 (Plain)	English, digits, basic symbols	160 characters	153 characters
UCS-2 (Unicode)	All languages, emojis, special symbols	70 characters	67 characters

tip

If your message contains even a single Unicode character (e.g., a Hindi letter or an emoji), the entire message switches to UCS-2 encoding, reducing the character limit. Plan your template length accordingly.

GSM-7 Character Set

The GSM-7 encoding supports the following characters without triggering Unicode mode:

Standard characters (1 character each):

Letters A-Z, a-z; digits 0-9; and symbols: @ $ _ ! " # % & ' ( ) * + , - . / : ; < = > ? space

Extended characters (2 characters each):

| ^ { } [ ] ~ \ €

warning

Extended GSM-7 characters like {, }, [, ], \, ~, ^, |, and the Euro sign (€) consume 2 character positions each. Account for this when calculating message length.

When to Use Unicode

Use Unicode encoding when your message contains:

• Regional Indian languages -- Hindi (Devanagari), Tamil, Telugu, Kannada, Malayalam, Bengali, Gujarati, Marathi, Odia, Punjabi (Gurmukhi)
• Arabic, Chinese, Japanese, Korean -- Any non-Latin script
• Special symbols -- Characters outside the GSM-7 set
• Emojis -- All emoji characters require Unicode encoding

Examples

Hindi (Devanagari):

आपका OTP 123456 है। इसे किसी के साथ साझा न करें।

Tamil:

உங்கள் OTP 123456. யாரிடமும் பகிர வேண்டாம்.

Mixed (Hindi + English):

Dear ग्राहक, आपका order #12345 ship हो गया है।

Sending Unicode SMS via API

Set the EncodingType parameter to unicode when sending via the Send SMS API:

curl -X POST "https://<api_key>:<api_token>@api.exotel.com/v1/Accounts/<account_sid>/Sms/send" \
  -d "From=EXOTL" \
  -d "To=+919876543210" \
  -d "Body=आपका OTP 123456 है। इसे किसी के साथ साझा न करें।" \
  -d "DltEntityId=1234567890123" \
  -d "DltTemplateId=1107160000000012345" \
  -d "EncodingType=unicode"

warning

You must set EncodingType=unicode explicitly. If you send Unicode content with EncodingType=plain (the default), the non-Latin characters may be garbled or the message may fail.

Via the Dashboard

1. Navigate to App Bazaar > SMS > Send SMS.
2. Select your sender ID.
3. Choose a Unicode-approved DLT template.
4. Enter or paste your message in the regional language.
5. The dashboard automatically detects Unicode content and sets the encoding.

Character Counting

Single SMS

Encoding	Max Characters
GSM-7	160
Unicode	70

Concatenated (Long) SMS

When a message exceeds the single SMS limit, it is split into segments. Each segment reserves space for a concatenation header:

Encoding	Segment 1	Segment 2+	Characters per Segment
GSM-7	153 usable	153 usable	153 per segment
Unicode	67 usable	67 usable	67 per segment

Segment Calculation Examples

Message Length (Unicode)	Segments	Billing Units
1-70 characters	1	1
71-134 characters	2	2
135-201 characters	3	3
202-268 characters	4	4

For detailed information on concatenated messaging, see Long SMS.

DLT Templates for Unicode

When registering templates on the DLT portal for Unicode messages:

Step 1: Select Unicode Content Type

When creating the template on the DLT portal:

1. Go to Templates > Add New Template.
2. Set Content Type to Unicode.
3. Enter the template body in the regional language.
4. Use {#var#} for variable placeholders, just like plain-text templates.

Step 2: Template Example

प्रिय {#var#}, आपका ऑर्डर #{#var#} शिप कर दिया गया है। ट्रैक करें: {#var#}

Step 3: Submit for Approval

Submit the Unicode template for DLT approval. Approval timelines are the same as plain-text templates (1-3 business days).

tip

Register both a plain-text and a Unicode version of important templates. This gives you flexibility to send in English or regional languages depending on the customer's preference.

Encoding Detection

Exotel provides automatic encoding detection in the dashboard, but when using the API, you should explicitly set the encoding type:

Scenario	Recommended EncodingType
English-only message	plain
Hindi, Tamil, or other regional language	unicode
Mixed English and regional	unicode
Message with emojis	unicode

Billing

Unicode SMS is billed per segment, the same as plain-text SMS. However, because Unicode messages have lower character limits per segment, a message of equal length costs more in Unicode:

Message	GSM-7 Segments	Unicode Segments
100 characters (English)	1	2
150 characters (English)	1	3
50 characters (Hindi)	N/A	1
100 characters (Hindi)	N/A	2

See SMS Pricing for per-segment rates.

Best Practices

1. Keep Unicode messages short -- With only 70 characters per segment, every character counts. Keep messages concise.
2. Always set EncodingType -- Explicitly set EncodingType=unicode in API calls to avoid encoding errors.
3. Register Unicode DLT templates -- Ensure your DLT templates are registered with the Unicode content type.
4. Test thoroughly -- Test Unicode messages on multiple devices and operators to verify correct rendering.
5. Calculate segments beforehand -- Use the character count to estimate billing before sending large campaigns.
6. Avoid mixing scripts unnecessarily -- Mixing English and regional scripts in the same message still triggers Unicode encoding for the entire message.
7. Provide language preference -- Where possible, store and respect customer language preferences to send messages in their preferred language.

Common Issues

Issue	Cause	Resolution
Garbled characters	EncodingType not set to unicode	Set EncodingType=unicode in the API call
Message too long	Unicode character limit exceeded	Shorten the message or split into multiple messages
Template mismatch	DLT template registered as plain text	Re-register the template with Unicode content type
Higher billing	Unicode uses more segments	Shorten messages to reduce segment count

Next Steps

• Long SMS -- Understand concatenated SMS and segment billing
• SMS Templates -- Register Unicode templates
• SMS Pricing -- Per-segment pricing
• SMS API Reference -- API documentation