capacitor-sms-otp-send-verify — SMS + OTP for Ionic / Capacitor, a free Twilio Verify alternative

Capacitor plugin to send SMS, send and verify OTP codes from your Ionic / Capacitor app on iOS and Android — routed through your own Android phone. No Twilio, no Vonage Verify, no MessageBird. No per-OTP fees, no markups, no A2P 10DLC. Free 5-day trial at sms8.io — no card.

import { SmsOtp } from 'capacitor-sms-otp-send-verify';

await SmsOtp.configure({ apiKey: 'sk_xxx' });
await SmsOtp.sendOtp({ phone: '+14155550100' });
const { verified } = await SmsOtp.verifyOtp({ phone: '+14155550100', code: '482937' });

Why this instead of Twilio Verify?

| | Twilio Verify / Vonage Verify | Capacitor SMS8 plugin | |---|---|---| | Per-OTP cost | $0.05 – $0.10 each | $0 (flat $29/mo unlimited) | | A2P 10DLC paperwork | Required in the US | Not required — P2P SMS from a real SIM | | Sender ID | Short code / random LCN | Your real mobile number | | Setup time | Days | Minutes | | Native iOS Swift + Android Kotlin | Yes (separate SDKs) | Yes (one plugin) | | Free trial | None | 5 days unlimited, no card |

Install

npm install capacitor-sms-otp-send-verify
npx cap sync

Then in your Capacitor project:

npx cap copy ios
npx cap copy android

Done. The plugin's native iOS Swift and Android Kotlin bridges are compiled into your app automatically.

Quick start

1. Get a free API key

1. Sign up at sms8.io — 5-day trial, no card
2. Install the SMS8 Android app, pair your phone
3. Copy your API key from app.sms8.io/api.php

2. Configure the plugin

Call configure once, typically in your app's bootstrap or before the first send:

import { SmsOtp } from 'capacitor-sms-otp-send-verify';

await SmsOtp.configure({
  apiKey: process.env.SMS8_API_KEY,
  // baseUrl: 'https://mcp.sms8.io' (default, rarely needs override)
});

Production: never embed your master API key in the app bundle. Proxy through your backend and pass a short-lived token to the plugin.

3. Send an OTP

const result = await SmsOtp.sendOtp({
  phone: '+14155550100',
  length: 6,                                          // default 6
  template: 'Your YourApp code: {code}',              // optional
  expiresIn: 300,                                     // default 300s
  maxAttempts: 5,                                     // default 5
});
console.log('OTP id:', result.otpId, 'expires:', result.expiresAt);

4. Verify the code the user typed

const r = await SmsOtp.verifyOtp({ phone: '+14155550100', code: '482937' });
if (r.verified) {
  // Welcome the user
} else {
  // r.error, r.attemptsLeft
}

5. Send a plain SMS

await SmsOtp.sendSms({ phone: '+14155550100', message: 'Order shipped!' });

Full Ionic example with auto-fill

import { IonInput, IonButton } from '@ionic/react';
import { useState } from 'react';
import { SmsOtp } from 'capacitor-sms-otp-send-verify';

export function VerifyPhone() {
  const [phone, setPhone] = useState('');
  const [code, setCode]   = useState('');
  const [stage, setStage] = useState<'phone' | 'code'>('phone');

  return stage === 'phone' ? (
    <>
      <IonInput
        type="tel"
        autocomplete="tel"
        value={phone}
        onIonChange={(e) => setPhone(e.detail.value!)}
        placeholder="+14155550100"
      />
      <IonButton onClick={async () => {
        await SmsOtp.sendOtp({ phone });
        setStage('code');
      }}>Send code</IonButton>
    </>
  ) : (
    <>
      <IonInput
        inputmode="numeric"
        autocomplete="one-time-code"
        maxlength={6}
        value={code}
        onIonChange={(e) => setCode(e.detail.value!)}
      />
      <IonButton onClick={async () => {
        const { verified } = await SmsOtp.verifyOtp({ phone, code });
        if (verified) navigate('/dashboard');
      }}>Verify</IonButton>
    </>
  );
}

The autocomplete="one-time-code" + inputmode="numeric" attributes activate iOS "From Messages" keyboard suggestion and Android SMS Retriever auto-fill automatically.

API

configure(options): Promise<void>

| Option | Type | Default | Notes | |---|---|---|---| | apiKey | string | — | Required. Get one free at https://sms8.io | | baseUrl | string | https://mcp.sms8.io | Override server (self-hosted MCP) |

sendSms(options): Promise<SendResult>

| Option | Type | Notes | |---|---|---| | phone | string | E.164 phone number | | message | string | SMS body | | deviceId? | number | Pin a specific paired Android | | simSlot? | string | Pick a SIM slot (multi-SIM) |

Returns { success, messageId, phone, error }.

sendOtp(options): Promise<SendOtpResult>

| Option | Type | Default | Notes | |---|---|---|---| | phone | string | — | E.164 phone | | length | number | 6 | Digits in the code (4-8) | | template | string | "Your verification code is {code}" | Use {code} placeholder | | expiresIn | number | 300 | Seconds until expiry | | maxAttempts | number | 5 | Verification attempts allowed | | deviceId? | number | — | Pin a paired Android | | simSlot? | string | — | Pick a SIM |

Returns { success, otpId, phone, expiresAt, expiresIn, error }.

verifyOtp(options): Promise<VerifyOtpResult>

| Option | Type | Notes | |---|---|---| | phone | string | Same phone you sent the OTP to | | code | string | Code the user typed |

Returns { success, verified, error, attemptsLeft }.

How it works

When you call SmsOtp.sendOtp from your Ionic/Capacitor JavaScript code:

1. On iOS → native Swift bridge in ios/Sources/... runs URLSession against https://mcp.sms8.io
2. On Android → native Kotlin bridge in android/src/... runs HttpURLConnection against https://mcp.sms8.io
3. In the browser → web fallback in dist/esm/web.js runs fetch against https://mcp.sms8.io

In all 3 cases the SMS8 backend queues the message, your paired Android phone polls SMS8, sends the SMS through its real SIM, and reports back. Typical round-trip: under 4 seconds.

Related packages

• cordova-plugin-sms-otp-send — same flow for Cordova
• react-sms-otp — React hook + components for web
• sms-otp-verify — same as react-sms-otp, alt name
• sms8-cli — terminal CLI
• sms8-mcp — MCP launcher for Claude Code / Cursor / Windsurf

Links

• Free signup: sms8.io
• Dashboard: app.sms8.io
• OTP API docs: sms8.io/sms-otp-verification-api-android
• Android app: sms8.io/sms-gateway-apk-android
• GitHub: github.com/1fancy/sms8-sms-gateway

License

MIT