Sinhala & Tamil SMS in Sri Lanka: Complete Guide to Unicode SMS (2026)

Who this guide is for: Marketers, developers, and business owners in Sri Lanka who want to reach Sinhala and Tamil-speaking customers in their own language — not in broken English.

The most well-crafted marketing message in the world fails if your customer cannot read it comfortably. Yet many Sri Lankan businesses still send every SMS in English, even though Sinhala and Tamil are the official languages of Sri Lanka and the languages most consumers think, read, and trust in first.

Times have changed. Modern gateways like TXTMSG support Unicode SMS, so you can deliver OTPs, appointment reminders, offers, and public alerts in Sinhala, Tamil, or English — all from the same dashboard or API.

This guide explains how Unicode SMS works, what it costs, the new 2026 Sender ID registration rules, and how to send your first native-language message today.

Why Sinhala & Tamil SMS Matters in Sri Lanka

Sri Lanka's mobile penetration exceeds 140%, which makes SMS the most direct line to nearly every adult in the country. But there is a language gap: most consumers are far more likely to respond to a message written in their mother tongue.

Consider a few everyday scenarios:

A bank alert about a suspicious transaction written in Sinhala is understood instantly. In English, it is often ignored — or worse, mistaken for a scam.
A tuition centre reminding parents of tomorrow's class in Tamil reaches the whole family, not just the English-literate member.
A clinic sending lab results in the patient's language reduces confusion and follow-up calls.

SMS is already the highest-open-rate channel available to Sri Lankan businesses. Sending it in the customer's language makes it more trusted, more relevant, and more likely to convert.

How Unicode SMS Works: 160 vs 70 Characters

Every SMS is capped at 140 bytes of payload per segment. The difference between English and Sinhala/Tamil SMS comes down to how each character is encoded:

Encoding	Bits per character	Characters per segment	Typical use
GSM-7 (standard alphabet)	7 bits	160 characters	English, numbers, basic punctuation
UCS-2 / Unicode	16 bits	70 characters	Sinhala, Tamil, emoji, other scripts

Why 70? 140 bytes ÷ 2 bytes per Unicode character = 70 characters. That is the maximum that fits in a single SMS segment.

What happens when you exceed 70 characters? The message is automatically split into multiple segments (concatenated SMS) and re-joined on the phone. The catch: each segment is billed separately. A 140-character Sinhala message costs the same as two SMS.

Rule of thumb: keep Unicode SMS under 70 characters wherever possible. You save money, and short messages perform better anyway.

The Cost Math: What Unicode SMS Really Costs

TXTMSG pricing applies per segment, exactly the same for English and Unicode SMS:

Plan	Price per SMS segment
Starter	LKR 1.00
Growth	LKR 0.85
Business	LKR 0.70
Enterprise	LKR 0.59

Worked example — a 90-character Sinhala promotional message:

90 characters > 70-character limit → split into 2 segments
At the Business rate: 2 × LKR 0.70 = LKR 1.40 per recipient
Sent to 1,000 customers: LKR 1,400 total

Compare that with the same message trimmed to 60 characters: 1 segment × LKR 0.70 × 1,000 = LKR 700 — half the cost, and often a better conversion rate because the message is tighter.

Sinhala and Tamil scripts are more character-dense than English, so concise copywriting matters even more in native-language campaigns.

When to Use Sinhala/Tamil vs English

Use case	Best language	Notes
OTP / security codes	English + numbers	Numeric codes are universal; keep instructions bilingual
Bank & payment alerts	Sinhala / Tamil	Trust-critical; native language prevents scam confusion
Healthcare & lab results	Sinhala / Tamil	Clarity reduces anxiety and follow-up calls
School & tuition reminders	Sinhala / Tamil	Reaches parents, not just students
Emergency / public health alerts	Sinhala / Tamil	Comprehension is safety-critical
Retail & F&B promotions	Sinhala / Tamil	Higher response than English for mass-market brands
Premium / expat hospitality	English	Match the audience's expectation
B2B technical communication	English	Business language of record

The winning pattern for most businesses: send transactional and trust messages in the customer's language, and segment your marketing list by language preference so each customer receives the variant they read best.

How to Send Sinhala & Tamil SMS with TXTMSG

Option 1: The Campaign Manager (no code)

Log in to the TXTMSG dashboard
Compose your message in Sinhala, Tamil, or English — Unicode is supported on every plan
TXTMSG handles the UCS-2 encoding and segment splitting automatically
Send and track delivery reports as usual

Option 2: The REST API

The same sms/send endpoint accepts Unicode text — no special parameters needed:

POST https://sms.txtmsg.lk/api/v3/sms/send
Authorization: Bearer TXTMSG_API_KEY
Content-Type: application/json

{
  "recipient": "+94771234567",
  "sender_id": "HEALTHPLUS",
  "type": "plain",
  "message": "ආයුබෝවන්! ඔබේ OTP කේතය: 8842"
}

And the Tamil equivalent:

{
  "recipient": "+94771234567",
  "sender_id": "HEALTHPLUS",
  "type": "plain",
  "message": "வணக்கம்! உங்கள் OTP: 8842"
}

TXTMSG encodes, segments, and routes Unicode automatically, so your application code stays identical whether you send English, Sinhala, or Tamil.

Sender ID Registration: The 2026 Deadline You Need to Know

This is the compliance change to plan for in 2026. Per the Sri Lanka SMS guidelines published for the local market:

Dialog, Etisalat, and Hutchison now require Sender ID registration. From 29 July 2026, messages sent with unregistered Sender IDs to these networks will be blocked.
Mobitel restricts registered Sender IDs to OTP, OTT, and transactional traffic (e.g. banking and payment messages). Promotional content sent through a registered Sender ID on Mobitel will be blocked by the operator.

Practical implications:

If your OTP or transactional flow uses an alphanumeric Sender ID (like BANKALERT), register it before the deadline — unregistered traffic to Dialog, Etisalat, and Hutchison stops on 29 July 2026.
If you run promotional campaigns, confirm your Sender ID and message type are approved for the networks you target.
TXTMSG handles the Sender ID registration workflow with Sri Lankan operators for you.

Action item: if you have not yet registered your Sender IDs with the operators, start the process now. Registration takes time, and the block date does not move.

6 Best Practices for Sinhala & Tamil SMS

1. Keep it under 70 characters

One segment, one bill, maximum deliverability. A tight 60-character message beats a rambling 140-character one every time.

2. Offer opt-out in the customer's language

Sri Lankan regulations require promotional SMS to include an opt-out. Write "Reply STOP" — and consider adding the local-language equivalent so it is understood.

3. Segment your list by language

Tag contacts as Sinhala, Tamil, or English and send each group the variant they read best. A single English blast to a mixed list is a wasted opportunity.

4. Test on a real handset first

Unicode rendering and segment boundaries can surprise you. Send a trial to a real Dialog or Mobitel number before a full campaign.

5. Use bilingual templates for OTP

Keep codes numeric and pair them with short bilingual instructions. Example: "Your OTP / ඔබේ OTP: 8842" — clarity without extra segments.

6. A/B test against English

Run the same offer in English and Sinhala for a week and compare replies. Most Sri Lankan mass-market brands see higher engagement from the native-language variant.

FAQ

Can I really send Sinhala and Tamil in an SMS?

Yes. Unicode SMS supports Sinhala script (e.g. ආයුබෝවන්) and Tamil script (e.g. வணக்கம்) exactly as typed. TXTMSG supports Unicode on every plan.

How many characters fit in one Unicode SMS?

70 characters per segment, versus 160 for English. Longer messages are split into multiple segments and billed per segment.

Does Unicode SMS cost more?

Per segment, no — the price is identical. But a message over 70 characters becomes 2+ segments, so a long Sinhala message effectively costs more than a short English one. Keep it concise.

Is native-language SMS legal in Sri Lanka?

Yes, subject to the same rules as English SMS: explicit consent for promotional messages, an opt-out option, and DNC registry scrubbing. TXTMSG's Smart Blacklist and DNC handling apply automatically.

Do emoji count as Unicode?

Yes. Emoji also use 16-bit encoding, so they consume the same 70-character budget as Sinhala and Tamil.

What about the July 2026 Sender ID change?

From 29 July 2026, unregistered Sender IDs are blocked on Dialog, Etisalat, and Hutchison networks. Register your Sender ID with the operators in advance — TXTMSG assists with the workflow.

Start Sending Sinhala & Tamil SMS Today

Sign up for a free TXTMSG account, compose your first Sinhala or Tamil message in the Campaign Manager, or connect the API in minutes. Complimentary trial credits included — no credit card required.

Get Started with TXTMSG →

Sources and References:

Twilio — Sri Lanka SMS Guidelines (mobile country code 413; Sender ID registration requirement for Dialog, Etisalat, and Hutchison; 29 July 2026 unregistered-Sender-ID block; Mobitel OTP/OTT/transactional restriction) — twilio.com/en-us/guidelines/lk/sms (verified August 2026)
TXTMSG — Platform pricing and Unicode & Flash SMS feature across all plans — txtmsg.lk (verified August 2026)
Notify.lk — Enabling Sinhala and Tamil Unicode SMS sending for Sri Lanka (160 vs 70 character technical baseline) — notify.lk/blog (updated)
Constitution of the Democratic Socialist Republic of Sri Lanka — official language status of Sinhala and Tamil — parliament.lk
TXTMSG aggregated gateway data — SMS benchmarks and segmentation guidance, 2026

TXTMSG Team

Contributor

Part of the TXTMSG team — dedicated to building reliable messaging infrastructure for businesses across Sri Lanka and beyond.