Universal Fallback
SMS Verification
Universal fallback verification via SMS. Works on any phone, anywhere in the world. Reverse OTP model - user sends to us.
How It Works
The universal option that works on every phone
Step 1
Create Request
Call our API with the phone number. We return a challenge code and SMS instructions.
Step 2
User Sends SMS
User sends an SMS with the challenge code to our verification number. Works on any phone.
Step 3
Instant Verification
We verify the SMS sender and return a cryptographic proof token via webhook.
API Integration
Simple SMS verification without the costs
1. Create Verification Request
curl -X POST https://api.proof.holdings/api/v1/verifications \
-H "Authorization: Bearer pk_live_YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"type": "phone",
"channel": "sms",
"identifier": "+37069199199"
}'2. Verify the Proof Token
# Poll for verification status
curl https://api.proof.holdings/api/v1/verifications/VERIFICATION_ID \
-H "Authorization: Bearer pk_live_YOUR_API_KEY"Response Example
{
"id": "507f1f77bcf86cd799439011",
"type": "phone",
"channel": "sms",
"status": "pending",
"identifier": "+37069199199",
"challenge": {
"code": "A7B3X9",
"expires_at": "2026-03-15T11:00:00Z",
"instruction": "Send 'A7B3X9' to one of the numbers below",
"sms_dids": {
"US": "+13129131102",
"EU": "+37052140180"
},
"suggested_region": "US"
},
"created_at": "2026-03-15T10:50:00Z"
}