Implementing SMS Authentication in Nuxt 3 Nitro Server Routes in 5 Minutes (Zero Paperwork)

Ever Been Blocked by Paperwork When Adding SMS Auth?

If you've ever tried building a toy project, a side hustle, or a startup MVP, you know the pain of integrating an SMS verification API. The major API vendors often ask for a mountain of paperwork: Business Licenses, Telecom Service Certificates, and a mandatory sender ID pre-registration process.

"I just want to send a 6-digit code for my side project..."

If that sounds like you, you're in the right place. Today, we'll learn how to implement SMS Authentication in Nuxt 3 Nitro Server Routes in under 5 minutes—with zero paperwork.

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Implementing SMS Auth with Nuxt 3 Nitro & EasyAuth

Nuxt 3 comes with an incredibly powerful built-in server engine called Nitro, making it super easy to build backend API routes. Combine this with EasyAuth, an instant-setup SMS API, and you can build a seamless verification flow in minutes.

1. Environment Variables Setup

First, add your EasyAuth API key to the .env file at the root of your project.

EASYAUTH_API_KEY=your_api_key_here

Next, expose this environment variable to your application using nuxt.config.ts.

export default defineNuxtConfig({
  runtimeConfig: {
    easyAuthApiKey: process.env.EASYAUTH_API_KEY
  }
})

2. Send OTP Endpoint (/api/send)

Let's create a server route in the server/api directory to handle sending the SMS code.
Create server/api/auth/send.post.ts:

export default defineEventHandler(async (event) => {
  const body = await readBody(event);
  const config = useRuntimeConfig();

  if (!body.phoneNumber) {
    throw createError({ statusCode: 400, statusMessage: 'Phone number is required.' });
  }

  try {
    const response = await $fetch('https://api.easyauth.kr/send', {
      method: 'POST',
      headers: {
        'Authorization': `Bearer ${config.easyAuthApiKey}`,
        'Content-Type': 'application/json'
      },
      body: { to: body.phoneNumber }
    });

    return { success: true, message: 'OTP sent successfully.' };
  } catch (error) {
    throw createError({ statusCode: 500, statusMessage: 'Failed to send OTP.' });
  }
});

3. Verify OTP Endpoint (/api/verify)

Now, we need an endpoint to verify the code entered by the user.
Create server/api/auth/verify.post.ts:

export default defineEventHandler(async (event) => {
  const body = await readBody(event);
  const config = useRuntimeConfig();

  if (!body.phoneNumber || !body.code) {
    throw createError({ statusCode: 400, statusMessage: 'Phone number and code are required.' });
  }

  try {
    const response = await $fetch('https://api.easyauth.kr/verify', {
      method: 'POST',
      headers: {
        'Authorization': `Bearer ${config.easyAuthApiKey}`,
        'Content-Type': 'application/json'
      },
      body: { 
        to: body.phoneNumber,
        code: body.code
      }
    });

    return { success: true, message: 'Phone number verified successfully.' };
  } catch (error) {
    throw createError({ statusCode: 400, statusMessage: 'Invalid OTP code.' });
  }
});

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Tips & Best Practices

1. Rate Limiting: To prevent malicious users from draining your SMS credits, implement IP-based rate limiting on the /api/send endpoint. The nuxt-security module is highly recommended for this.
2. International Numbers: If you're building a global service, ensure your frontend properly formats the country code (e.g., +82) before sending the request to the Nitro backend.

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Conclusion: Start Instantly, Skip the Paperwork

When you're building an MVP or an indie project, speed is everything. Don't waste days waiting for document approvals and sender ID registrations.

By using [EasyAuth], developers get:

• Zero Paperwork: No business licenses or telecom certificates required.
• Auto Sender ID: Skip the pre-registration and start sending immediately.
• Affordable Pricing: Only 15-25 KRW per message (half the price of competitors).
• Free Trial: Sign up and get 10 free SMS credits to test out your integration.

Integrate SMS auth the easy way with just two endpoints (send and verify).