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Twilio SMS

Connect WPsigner with Twilio to send signing requests, confirmations, and reminders via SMS to your signers’ mobile phones.

Use Cases

Section titled “Use Cases”
ScenarioDescription
Remote signersReach signers who may not check email frequently by delivering signing links via SMS
Urgent documentsSend time-sensitive signing requests that demand immediate attention
Two-factor deliveryCombine email and SMS channels to ensure signing requests are received
Automated remindersNudge pending signers with SMS reminders to reduce turnaround time
Confirmation receiptsNotify signers via SMS the moment their signature is recorded
Completion alertsAlert all parties by text when every signer has completed the document

Prerequisites

Section titled “Prerequisites”
  • A Twilio account (free trial available)
  • A Twilio phone number with SMS capabilities
  • WPsigner v2.1.0 or later

Compatibility

Section titled “Compatibility”
ComponentMinimum VersionRecommended
WPsigner2.1.0Latest
WordPress5.86.4+
PHP7.48.1+
Twilio API2010-04-012010-04-01
TLS1.21.3
PHP Extensionscurl, jsoncurl, json, openssl

Setup Guide

Section titled “Setup Guide”

1. Create a Twilio Account

Section titled “1. Create a Twilio Account”
  1. Go to twilio.com and sign up
  2. Verify your email and phone number
  3. Free trial accounts include test credits

2. Get a Phone Number

Section titled “2. Get a Phone Number”
  1. In the Twilio Console, navigate to Phone Numbers → Manage → Buy a Number
  2. Select a number with SMS capabilities
  3. Note down the phone number (in E.164 format, e.g., +15551234567)

3. Copy Your Credentials

Section titled “3. Copy Your Credentials”
  1. From the Twilio Console Dashboard, locate:
    • Account SID — starts with AC followed by 32 characters
    • Auth Token — click the eye icon to reveal

4. Configure WPsigner

Section titled “4. Configure WPsigner”
  1. Go to WPsigner → Integrations
  2. Click Twilio SMS
  3. Enter your Account SID, Auth Token, and From Number
  4. Click Test Connection to verify
  5. Toggle Enable on
  6. Click Save Settings

Notification Events

Section titled “Notification Events”
EventTriggerRecipient
Signing RequestSigner added to documentSigner (if phone provided)
Signature RecordedSigner completes signatureSigner
Document CompleteAll signers finishedAll signers with phone numbers
ReminderAdmin-initiatedPending signer

Phone Number Format

Section titled “Phone Number Format”

All phone numbers must be in E.164 format:

FormatValid?
+15551234567Yes
+442071234567Yes
5551234567No — Missing country code
(555) 123-4567No — Formatting characters

Security

Section titled “Security”
MeasureDetails
Auth TokenEncrypted at rest (AES-256-GCM)
Account SIDStored in wp_options
API CommunicationHTTPS only (TLS 1.2+)
AJAX SecurityNonce + capability check + rate limiting
Rate Limiting5 tests/min, 10 saves/min per user

API Reference

Section titled “API Reference”

WPsigner uses the Twilio REST API:

POST https://api.twilio.com/2010-04-01/Accounts/{SID}/Messages.json
  • Authentication: HTTP Basic (Account SID : Auth Token)
  • Content-Type: application/x-www-form-urlencoded
  • Parameters: To, From, Body

Troubleshooting

Section titled “Troubleshooting”

”Connection failed” on test

Section titled “”Connection failed” on test”
  • Verify your Account SID starts with AC and is exactly 34 characters
  • Re-enter your Auth Token (it’s not displayed after saving)
  • Check your account status at twilio.com/console

SMS not received

Section titled “SMS not received”
  • Verify the recipient number is in E.164 format
  • Check your Twilio balance and trial limitations
  • Trial accounts can only send to verified numbers

Error code 21608

Section titled “Error code 21608”
  • Your Twilio number doesn’t have SMS capability
  • Purchase a number with SMS enabled

Comparison

Section titled “Comparison”
FeatureTwilio SMSWhatsAppTelegramSlack
TypeSMSBusiness APIBot APIWebhook
ReachAny phoneWhatsApp usersTelegram usersTeam channel
CostPer messagePer messageFreeFree
Rich formattingNoYesYes (HTML)Yes (Block Kit)
Action buttonsNoNoInline keyboardBlock actions
Setup complexityLowMediumLowLow

Next Steps

Section titled “Next Steps”