Slovakia SMS Best Practices, Compliance, and Features

Slovakia SMS Market Overview

Market Conditions: Slovakia has a mature mobile market with high SMS adoption rates. The country's telecommunications sector is served by major operators including Orange Slovakia, Slovak Telekom, and O2 Slovakia. While OTT messaging apps like WhatsApp and Facebook Messenger are popular, SMS remains a crucial channel for business communications, particularly for authentication and notifications. The market shows a relatively even split between Android and iOS devices, with Android having a slight edge in market share.

Key SMS Features and Capabilities in Slovakia

Slovakia supports most standard SMS features including concatenated messages and alphanumeric sender IDs, though two-way SMS functionality is limited.

Two-way SMS Support

Two-way SMS is not supported in Slovakia through most major SMS providers. This means businesses cannot receive replies to their messages through standard SMS APIs.

Concatenated Messages (Segmented SMS)

Support: Yes, concatenation is supported for messages exceeding standard length limits.
Message length rules: Standard SMS length is 160 characters for GSM-7 encoding, or 70 characters for Unicode (UCS-2).
Encoding considerations: Messages using GSM-7 encoding can be concatenated up to 153 characters per segment, while UCS-2 encoded messages allow 67 characters per segment.

MMS Support

MMS messages are automatically converted to SMS with an embedded URL link. This ensures compatibility across all devices while still allowing rich media content to be shared through a web interface.

Recipient Phone Number Compatibility

Number Portability

Number portability is available in Slovakia, allowing users to keep their phone numbers when switching carriers. This feature is fully supported and does not affect message delivery or routing.

Sending SMS to Landlines

Sending SMS to landline numbers is not supported in Slovakia. Attempts to send messages to landline numbers will result in delivery failure and may trigger error responses from the SMS API (e.g., error code 21614 for some providers).

Compliance and Regulatory Guidelines for SMS in Slovakia

As a member of the European Union, Slovakia follows GDPR and e-Privacy Directive requirements for SMS communications. The primary regulatory authority is the Office for Personal Data Protection of the Slovak Republic (Úrad na ochranu osobných údajov Slovenskej republiky).

Consent and Opt-In

Explicit Consent Requirements:

• Written or electronic consent must be obtained before sending marketing messages
• Consent must be freely given, specific, informed, and unambiguous
• Keep detailed records of when and how consent was obtained
• Purpose of messaging must be clearly stated during opt-in

HELP/STOP and Other Commands

• All marketing messages must include clear opt-out instructions
• STOP command must be supported in both Slovak and English
• Common Slovak keywords include:
  • STOP or ZASTAVIT for opt-out
  • POMOC or HELP for assistance
• Messages should be processed in both upper and lower case

Do Not Call / Do Not Disturb Registries

Slovakia does not maintain a centralized Do Not Call registry. However, businesses must:

• Maintain their own suppression lists
• Honor opt-out requests within 24 hours
• Keep records of opted-out numbers for at least 2 years
• Regularly clean contact lists to remove unsubscribed numbers

Time Zone Sensitivity

Slovakia observes Central European Time (CET/CEST). While there are no strict legal restrictions on SMS timing:

• Avoid sending messages between 20:00 and 08:00 local time
• Respect weekends and national holidays
• Emergency notifications are exempt from time restrictions

Phone Numbers Options and SMS Sender Types for in Slovakia

Alphanumeric Sender ID

Operator network capability: Fully supported
Registration requirements: No pre-registration required, dynamic usage allowed
Sender ID preservation: Sender IDs are preserved and displayed as-is to recipients

Long Codes

Domestic vs. International:

• Domestic long codes not supported
• International long codes supported but sender ID may be modified

Sender ID preservation: International long code sender IDs are typically replaced with generic alphanumeric IDs
Provisioning time: Immediate activation
Use cases: Transactional messaging, alerts, and notifications

Short Codes

Support: Not currently supported in Slovakia
Provisioning time: N/A
Use cases: N/A

Restricted SMS Content, Industries, and Use Cases

Restricted Industries and Content:

• Gambling and betting services (unless properly licensed)
• Adult content or services
• Cryptocurrency promotions
• Unauthorized financial services
• Political campaigning without proper disclaimers

Content Filtering

Known Carrier Filtering Rules:

• Messages containing certain keywords may be blocked
• URLs should be from reputable domains
• Avoid excessive capitalization and special characters

Best Practices to Avoid Filtering:

• Use clear, professional language
• Avoid URL shorteners
• Include company name in message
• Maintain consistent sending patterns

Best Practices for Sending SMS in Slovakia

Messaging Strategy

• Keep messages under 160 characters when possible
• Include clear call-to-action
• Use personalization tokens (recipient's name, relevant details)
• Maintain consistent brand voice

Sending Frequency and Timing

• Limit to 2-4 messages per month per recipient
• Respect Slovak holidays and cultural events
• Send during business hours (9:00-17:00)
• Space out bulk campaigns to avoid network congestion

Localization

• Primary language should be Slovak
• Consider including English for international audiences
• Use proper diacritical marks in Slovak text
• Respect local date formats (DD.MM.YYYY)

Opt-Out Management

• Process opt-outs in real-time
• Maintain centralized opt-out database
• Confirm opt-out with one final message
• Regular audit of opt-out list

Testing and Monitoring

• Test across all major Slovak carriers
• Monitor delivery rates by carrier
• Track engagement metrics
• Regular A/B testing of message content

SMS API integrations for Slovakia

Twilio

Twilio provides robust SMS capabilities for Slovakia through their REST API. Authentication uses account SID and auth token credentials.

import { Twilio } from 'twilio';

// Initialize client with your credentials
const client = new Twilio(
  process.env.TWILIO_ACCOUNT_SID,
  process.env.TWILIO_AUTH_TOKEN
);

// Function to send SMS to Slovakia
async function sendSlovakiaSMS(
  to: string,
  message: string,
  senderId: string
) {
  try {
    // Ensure number is in E.164 format for Slovakia (+421)
    const formattedNumber = to.startsWith('+421') ? to : `+421${to}`;
    
    const response = await client.messages.create({
      body: message,
      from: senderId, // Alphanumeric sender ID
      to: formattedNumber,
    });
    
    console.log(`Message sent successfully! SID: ${response.sid}`);
    return response;
  } catch (error) {
    console.error('Error sending message:', error);
    throw error;
  }
}

Sinch

Sinch offers SMS API access with service plan ID and API token authentication.

import { SinchClient } from '@sinch/sdk';

// Initialize Sinch client
const client = new SinchClient({
  servicePlanId: process.env.SINCH_SERVICE_PLAN_ID,
  apiToken: process.env.SINCH_API_TOKEN,
  region: 'europe-central1'
});

// Send SMS to Slovakia
async function sendSlovakiaSMS(
  recipientNumber: string,
  messageText: string
) {
  try {
    const response = await client.sms.send({
      to: [recipientNumber],
      message: messageText,
      from: 'YourBrand', // Alphanumeric sender ID
      delivery_report: 'summary'
    });
    
    console.log('Message batch ID:', response.batchId);
    return response;
  } catch (error) {
    console.error('Sinch SMS error:', error);
    throw error;
  }
}

MessageBird

MessageBird provides SMS capabilities with API key authentication.

import { MessageBirdClient } from 'messagebird';

// Initialize MessageBird client
const messagebird = new MessageBirdClient(
  process.env.MESSAGEBIRD_API_KEY
);

// Function to send SMS
async function sendSlovakiaSMS(
  to: string,
  message: string,
  originator: string
) {
  return new Promise((resolve, reject) => {
    messagebird.messages.create({
      originator: originator, // Your sender ID
      recipients: [to],
      body: message,
      datacoding: 'auto' // Automatic character encoding
    }, (err, response) => {
      if (err) {
        console.error('MessageBird error:', err);
        reject(err);
      } else {
        console.log('Message sent:', response.id);
        resolve(response);
      }
    });
  });
}

Plivo

Plivo offers SMS integration with auth ID and auth token authentication.

import { Client } from 'plivo';

// Initialize Plivo client
const client = new Client(
  process.env.PLIVO_AUTH_ID,
  process.env.PLIVO_AUTH_TOKEN
);

// Send SMS function
async function sendSlovakiaSMS(
  destination: string,
  message: string,
  senderId: string
) {
  try {
    const response = await client.messages.create({
      src: senderId,
      dst: destination,
      text: message,
      url_strip_query_params: false
    });
    
    console.log('Message UUID:', response.messageUuid);
    return response;
  } catch (error) {
    console.error('Plivo error:', error);
    throw error;
  }
}

API Rate Limits and Throughput

• Default rate limits vary by provider (typically 1-10 messages per second)
• Implement exponential backoff for retry logic
• Use batch APIs for high-volume sending
• Consider queue systems like Redis or RabbitMQ for large campaigns

Error Handling and Reporting

• Implement comprehensive error logging
• Monitor delivery receipts (DLRs)
• Track common error codes:
  • Invalid number format
  • Network errors
  • Rate limit exceeded
  • Invalid sender ID

Recap and Additional Resources

Key Takeaways

1. Compliance Priorities

   • GDPR compliance is mandatory
   • Obtain explicit consent
   • Honor opt-out requests promptly
   • Maintain accurate records

2. Technical Considerations

   • Use alphanumeric sender IDs
   • Implement proper error handling
   • Monitor delivery rates
   • Test across all carriers

3. Best Practices

   • Localize content appropriately
   • Respect time zones and quiet hours
   • Maintain clean contact lists
   • Regular testing and monitoring

Next Steps

1. Review the Slovak Office for Personal Data Protection guidelines
2. Implement proper consent management systems
3. Set up monitoring and reporting tools
4. Test message delivery across all major carriers

Additional Resources

• Slovak Telecommunication Office
• Office for Personal Data Protection
• GDPR Guidelines for SMS Marketing
• Slovak Direct Marketing Association