USDT-TRC20 prepaid · pay as you go

One API for SMS, OTP, Voice & Email

Send SMS & email OTP, run marketing campaigns and power cloud hotlines — all billed from a single USDT prepaid wallet. Multi-tenant, developer-first, in Vietnamese, English and Chinese.

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No monthly fees · top up with USDT (TRC20)

api.hqotp.com/api/v1/otp/request

curl https://api.hqotp.com/api/v1/otp/request \
  -H "x-api-key: hqk_••••••••" \
  -H "content-type: application/json" \
  -d '{ "channel": "SMS", "purpose": "LOGIN",
        "target": "+84xxxxxxxxx" }'

200 OK
{
  "success": true,
  "data": { "requestId": "otp_9f2c…",
            "expiresAt": "…",
            "target": "•••••••321" }
}

5 in one

Channels

USDT prepaid

Billing

VI · EN · 中文

Languages

REST + Webhooks

Integration

Everything you need to reach customers

One platform, one balance — five channels.

SMS OTP

One-time codes with hashing, TTL, attempt limits and automatic provider failover.

SMS Marketing

Campaigns with contact lists, dedupe, suppression and budget control.

Email OTP

Verification codes over email with the same security guarantees.

Email Marketing

Bulk email with consent, quiet hours and delivery tracking.

Hotline / Cloud Calling

Virtual numbers, call routing and detailed call records.

USDT Prepaid Wallet

Top up with USDT-TRC20; every send is metered against a double-entry ledger.

Built for developers, secured for finance

Bank-grade security

Argon2 + 2FA, encrypted credentials, append-only audit log and no floating-point money.

Developer-first API

REST API, scoped API keys, signed webhooks, OpenAPI docs and idempotency keys.

Transparent billing

Prepaid USDT, per-message price snapshots and a fully reconcilable ledger.

Multi-language

Full Vietnamese, English and Chinese across the app, emails and messages.

Start sending in minutes

Create an account, top up USDT, and go live.

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