Skip to main content
This guide covers SMS messaging, character limits, concatenation, geo permissions, and delivery.

​
Character Limits

​
GSM-7 Encoding (Standard Characters)

Message LengthSegmentsCharacters per Segment
1-160 characters1160
161-1600 charactersMultiple153 (7 chars for header)
Maximum: 1,600 characters (splits into ~11 segments)

​
Unicode Encoding (Special Characters)

Message LengthSegmentsCharacters per Segment
1-70 characters170
71+ charactersMultiple67 (3 chars for header)
When any Unicode character appears in your message, the entire message uses UCS-2 encoding.

​
Automatic Encoding

Enable automatic encoding to replace Unicode characters with GSM-7 equivalents:
  1. Navigate to Messaging > Settings > Other Settings
  2. Enable Auto-replace
This prevents accidental segmentation from smart quotes, em dashes, etc.

​
SMS Concatenation

Long messages are automatically split and reassembled.

​
How It Works

  1. Plivo splits message into segments
  2. Concatenation header added to each segment
  3. Carrier reassembles at delivery
  4. Recipient sees single message

​
Billing

Each segment is billed separately. A 200-character message = 2 segments = 2x SMS cost.

​
Send SMS

​
Single Message

curl -X POST "https://api.plivo.com/v1/Account/{auth_id}/Message/" \
  -u "{auth_id}:{auth_token}" \
  -H "Content-Type: application/json" \
  -d '{
    "src": "14151234567",
    "dst": "14157654321",
    "text": "Hello from Plivo!"
  }'

​
Bulk Messages

Send to multiple recipients in one request: 
curl -X POST "https://api.plivo.com/v1/Account/{auth_id}/Message/" \
  -u "{auth_id}:{auth_token}" \
  -H "Content-Type: application/json" \
  -d '{
    "src": "14151234567",
    "dst": "14157654321<14158765432<14159876543",
    "text": "Bulk message to multiple recipients"
  }'
Separate destinations with < character.

​
Receive SMS

​
Configure Inbound URL

  1. Create an application with a message_url
  2. Assign a Plivo number to the application
  3. Plivo POSTs inbound messages to your URL

​
Message Delivery Flow

StageDescription
ReceivedPlivo receives from carrier (charged)
DeliveredSuccessfully posted to your message_url
UndeliveredFailed to deliver to your URL
If message_url is not configured, messages remain in “received” status.

​
Source Number Requirements

​
US and Canada

  • Must use Plivo number as source
  • Non-Plivo numbers not permitted (telecom regulations)

​
International

  • Dynamic sender IDs may be used
  • Delivery not guaranteed for non-Plivo numbers
  • Check country coverage for sender ID support

​
Geo Permissions

Control which countries can receive your SMS.

​
Default Enabled Countries

  • United States
  • United Kingdom
  • India

​
Configure Geo Permissions

  1. Navigate to Messaging > Settings > Geo Permissions
  2. Enable/disable countries as needed
  3. Set messages-per-hour fraud thresholds

​
Subaccount Permissions

By default, subaccounts inherit main account settings. Override for subaccount:
  1. Go to Geo Permissions
  2. Select subaccount from dropdown
  3. Customize settings
  4. Subaccount shows “Overridden” tag
Remove override:
  1. Select overridden subaccount
  2. Click Remove Override

​
Error Code 450

Messages to disabled countries fail with error 450: “destination country barred.”

​
SMS Pumping Protection

SMS pumping is fraud where attackers flood OTP fields with fake requests to premium numbers.

​
Protection Features

Enabled by default for all accounts:
  • Automated traffic analysis
  • Suspicious pattern detection
  • Alerts for unusual activity

​
Prevention Best Practices

  • Enable Geo Permissions
  • Set rate limits on OTP endpoints
  • Implement CAPTCHA on forms
  • Monitor traffic patterns
  • Use Plivo’s fraud detection tools

​
Access Message Content

Message content is stored for 7 days.

​
View in Console

  1. Navigate to Messaging > Logs
  2. Search by timeframe or UUID
  3. View message details
Note: Only available if data logging is enabled.

​
Authorize Content Access

Allow Plivo support to view content for debugging:
  • Helps identify spam filter triggers
  • Assists with delivery issues
  • Enables content policy review

​
Insufficient Balance

When balance is insufficient:
  1. Messages fail with error code 900
  2. API requests fail for 2 minutes with “Insufficient Credit”
  3. Queued messages continue to fail until recharged
Set up auto-recharge to prevent interruptions.

​
Carrier Surcharges

​
Toll-Free Surcharges (US)

CarrierSurcharge per Segment
Verizon$0.0025
T-MobileVaries
AT&TVaries
Surcharges appear as separate invoice line items.

​
Number Lookup API

Get information about phone numbers:
  • Local and E.164 formatting
  • Carrier information
  • Caller ID name (CNAM)
See Lookup API documentation.