How to Send Bulk SMS: Complete Guide with API & Dashboard

Sending SMS messages to thousands of customers at once might seem daunting, but it doesn't have to be. Whether you're announcing a flash sale, sending appointment reminders, or keeping customers informed about their orders, bulk SMS is one of the most effective communication channels available.

In this guide, we'll walk you through everything you need to know about sending bulk SMS - from using a simple dashboard interface to integrating with our powerful API.

What is Bulk SMS?

Bulk SMS (also known as mass texting or SMS broadcasting) is the practice of sending a single message to a large group of recipients simultaneously. Unlike individual messages, bulk SMS is designed for:

• Marketing campaigns - Promotions, sales, new product launches
• Transactional notifications - Order updates, shipping alerts
• Alerts and reminders - Appointments, events, deadlines
• Internal communications - Team updates, emergency notifications

According to Gartner, SMS has a 98% open rate compared to just 20% for email, making it an incredibly effective channel for time-sensitive communications.

Before You Start: What You'll Need

Before sending your first bulk SMS campaign, make sure you have:

A Zavu account - Sign up for free if you haven't already

A phone number - You can purchase one directly from our dashboard

Your contact list - Phone numbers in E.164 format (e.g., +14155551234)

Your message content - Keep it concise and valuable

For US messaging, you'll also need to be registered for A2P 10DLC - but don't worry, we handle that for you automatically.

Method 1: Using the Dashboard (No Code Required)

The easiest way to send bulk SMS is through our visual dashboard. Here's how:

Step 1: Create a New Broadcast

Log in to your Zavu Dashboard

Navigate to Broadcasts in the left sidebar

Click Create Broadcast

Step 2: Configure Your Campaign

Give your broadcast a descriptive name that helps you identify it later:

• Good: "Black Friday Sale 2025 - VIP Customers"
• Not so good: "Campaign 1"

Select SMS as your channel and choose which sender (phone number) to use.

Step 3: Write Your Message

Compose your message in the text editor. You can use personalization variables to make each message unique:

text
Hi {{name}}, don't miss our exclusive Black Friday deals!
Use code FRIDAY25 for 25% off your next order.
Shop now: https://yourstore.com/sale

Reply STOP to unsubscribe.

Pro tip: Keep your message under 160 characters when possible to avoid splitting into multiple segments. Learn more about GSM-7 encoding and character limits.

Step 4: Add Your Contacts

You have several options for adding recipients:

• Upload CSV - Import a spreadsheet with phone numbers and personalization data
• Manual entry - Add individual numbers directly
• Import from contacts - Select from your existing contact list

Your CSV should look like this:

csv
phone,name,order_id
+14155551234,John,ORD-001
+14155555678,Sarah,ORD-002
+14155559012,Mike,ORD-003

Step 5: Review and Send

Before sending, you'll see:

• Total number of recipients
• Estimated cost
• Message preview with personalization

You can either:

• Send immediately - Start the broadcast right away
• Schedule for later - Pick a specific date and time

Step 6: Monitor Progress

Once your broadcast starts, you can track progress in real-time:

• Messages sent vs. pending
• Delivery confirmations
• Failed deliveries with reasons
• Opt-out requests

Method 2: Using the Broadcasts API

For developers who need programmatic control, our Broadcasts API offers complete flexibility. Here's how to send bulk SMS with code:

Step 1: Install the SDK

bash
# Using npm
npm install @zavudev/sdk

# Using bun
bun add @zavudev/sdk

Step 2: Create a Broadcast

typescript
import Zavudev from "@zavudev/sdk";

const client = new Zavu(); // Uses ZAVU_API_KEY from environment

// Create a new broadcast campaign
const broadcast = await client.broadcasts.create({
  name: "Black Friday Sale 2025",
  channel: "sms",
  text: "Hi {{name}}, don't miss our Black Friday deals! Use code FRIDAY25 for 25% off. Reply STOP to unsubscribe.",
});

console.log("Broadcast created: " + broadcast.id);
// Output: Broadcast created: brd_abc123

Step 3: Add Contacts

You can add up to 1,000 contacts per API call:

typescript
// Add contacts with personalization variables
const result = await client.broadcasts.contacts.add(broadcast.id, {
  contacts: [
    {
      recipient: "+14155551234",
      templateVariables: { name: "John" }
    },
    {
      recipient: "+14155555678",
      templateVariables: { name: "Sarah" }
    },
    {
      recipient: "+14155559012",
      templateVariables: { name: "Mike" }
    }
  ]
});

console.log("Added: " + result.added + ", Duplicates: " + result.duplicates + ", Invalid: " + result.invalid);

For larger lists, batch your requests:

typescript
// Helper function for batching
async function addContactsInBatches(broadcastId: string, contacts: any[], batchSize = 1000) {
  for(let i = 0; i < contacts.length; i += batchSize) {
    const batch = contacts.slice(i, i + batchSize);
    await client.broadcasts.contacts.add(broadcastId, { contacts: batch });
    console.log("Added batch " + (Math.floor(i / batchSize) + 1));
  }
}

Step 4: Send the Broadcast

typescript
// Send immediately
await client.broadcasts.send(broadcast.id);

// Or schedule for later
await client.broadcasts.send(broadcast.id, {
  scheduledAt: "2025-11-29T09:00:00Z" // Black Friday, 9 AM UTC
});

Step 5: Monitor Progress

typescript
// Check broadcast progress
const progress = await client.broadcasts.progress(broadcast.id);

console.log("Status: " + progress.status);
console.log("Progress: " + progress.percentComplete + "%");
console.log("Delivered: " + progress.delivered);
console.log("Failed: " + progress.failed);
console.log("Pending: " + progress.pending);

Complete Example

Here's a full working example:

typescript
import Zavudev from "@zavudev/sdk";

async function sendBlackFridayCampaign() {
  const client = new Zavu();

  // 1. Create the broadcast
  const broadcast = await client.broadcasts.create({
    name: "Black Friday Sale 2025",
    channel: "sms",
    text: "Hi {{name}}, Black Friday is here! Get 25% off with code FRIDAY25. Shop: https://yourstore.com/sale. Reply STOP to opt out."
  });

  // 2. Add your contacts
  const customers = [
    { recipient: "+14155551234", templateVariables: { name: "John" } },
    { recipient: "+14155555678", templateVariables: { name: "Sarah" } },
    { recipient: "+14155559012", templateVariables: { name: "Mike" } },
    // ... more customers
  ];

  await client.broadcasts.contacts.add(broadcast.id, { contacts: customers });

  // 3. Schedule for Black Friday at 9 AM
  await client.broadcasts.send(broadcast.id, {
    scheduledAt: "2025-11-29T09:00:00Z"
  });

  console.log("Campaign scheduled! ID: " + broadcast.id);

  // 4. Check progress later
  const progress = await client.broadcasts.progress(broadcast.id);
  console.log("Status: " + progress.status + " - " + progress.percentComplete + "% complete");
}

sendBlackFridayCampaign().catch(console.error);

Best Practices for Bulk SMS

1. Respect Character Limits

SMS messages using standard GSM-7 encoding support 160 characters per segment. Messages with special characters (emojis, certain accents) switch to Unicode, reducing the limit to 70 characters.

Recommendation: Keep messages under 160 characters when possible to minimize costs.

2. Always Include Opt-Out Instructions

In most countries, you're legally required to provide a way for recipients to unsubscribe. Always include:

text
Reply STOP to unsubscribe.

Zavu automatically handles opt-out requests and removes unsubscribed contacts from future campaigns.

3. Personalize Your Messages

Personalized messages see significantly higher engagement. Use template variables like:

• {{name}} - Recipient's name
• {{order_id}} - Order number
• {{appointment_date}} - Scheduled date

4. Send at the Right Time

According to HubSpot research:

• Best days: Tuesday, Wednesday, Thursday
• Best times: 10 AM - 12 PM and 2 PM - 3 PM local time
• Avoid: Early mornings, late nights, weekends (unless urgent)

5. Segment Your Audience

Don't send the same message to everyone. Use customer segmentation to create targeted campaigns:

• VIP customers get early access
• New customers get welcome offers
• Inactive customers get re-engagement messages

6. Test Before Sending

Always send a test message to yourself or your team before launching a campaign. Check for:

• Personalization variables rendering correctly
• Links working properly
• Message displaying well on mobile
• Character count within limits

Understanding Costs

Bulk SMS pricing varies by:

• Destination country - US messages typically cost $0.01-0.02 each
• Message length - Long messages may be split into multiple segments
• Volume - Higher volumes often qualify for better rates

Zavu provides transparent pricing with no hidden fees. You can see the estimated cost before sending any campaign.

Compliance Considerations

United States

For US messaging, you need:

• A2P 10DLC registration (we handle this for you)
• TCPA compliance - Prior express written consent for marketing
• Clear opt-out mechanism

Europe

For EU messaging:

• GDPR compliance - Explicit consent required
• Clear identification of sender
• Right to withdraw consent

Canada

• CASL compliance - Express or implied consent
• Sender identification
• Unsubscribe mechanism

Advanced Features

Smart Routing

When you use the smart channel option, Zavu automatically selects the best channel for each recipient:

typescript
const broadcast = await client.broadcasts.create({
  name: "Multi-channel Campaign",
  channel: "smart", // Automatically choose SMS, WhatsApp, or Email
  text: "Your message here..."
});

This can significantly reduce costs by routing messages through the most cost-effective channel available.

Webhooks for Real-Time Updates

Set up webhooks to receive real-time notifications about your broadcast:

• Message delivered
• Message failed
• Contact opted out
• Broadcast completed

Learn more in our API documentation.

Troubleshooting Common Issues

Messages Not Delivering

Check phone number format - Must be E.164 (e.g., +14155551234)

Verify sender registration - US numbers need 10DLC registration

Check carrier filtering - Some content may trigger spam filters

High Failure Rates

• Invalid numbers - Clean your list before sending
• Carrier issues - Try sending at different times
• Content filtering - Avoid spam-like language

Slow Delivery

Delivery speed depends on your 10DLC trust score. Higher scores = faster throughput.

Next Steps

Ready to send your first bulk SMS campaign? Here's what to do:

Create a free account - No credit card required

Get a phone number - Purchase directly from the dashboard

Import your contacts - Upload your customer list

Create your first broadcast - Use the dashboard or API

Have questions? Check out our complete API documentation or contact our support team.

Related Resources

• What is A2P 10DLC? - Understanding US SMS compliance
• GSM-7 Character Encoding - Why character counts matter
• Customer Segmentation - Target your messages effectively
• RCS Messaging - The future of business texting
• API Documentation - Complete API reference