How to Integrate Sinch with V0

Start by creating a Sinch account at sinch.com. The registration process is quick and you get trial credits immediately — enough to test sending a few dozen SMS messages before needing to upgrade. After logging in, navigate to the Customer Dashboard at dashboard.sinch.com. You need three pieces of information for the SMS API. First, your Service Plan ID — find this under SMS → REST API in the left sidebar. The Service Plan ID is a long alphanumeric string. Second, your API Token — this is shown alongside the Service Plan ID on the same page. The API Token is your password for authenticating API requests; treat it like a secret key and never share it. Third, a virtual phone number to send messages from — provision one from the Numbers section of the dashboard. In the US, you can use a long code (regular 10-digit number) or a short code for high-volume messaging. Sinch also provides a Sinch Number (virtual number) that you use as the 'from' address in your SMS sends. This is not a secret — it is just a phone number — but you should still store it as an environment variable so you can change it without redeploying code. If you plan to use Sinch's Verification API (for OTP flows), you also need to create a Verification application in the dashboard under Verification → Apps. This gives you a separate Application Key and Application Secret for verification operations. The Verification API uses different credentials than the SMS API, so keep them organized in your environment variables.

Use V0 to generate the front-end component for your messaging or notification flow. The design depends on your use case, but the key requirement is that the component makes a request to your Next.js API route rather than calling Sinch directly. For a simple SMS notification form, V0 should generate a form with a phone number input (with proper international format hints), a message textarea, and a submit button. The form should validate that the phone number looks valid before submitting. V0 generates excellent form validation with React Hook Form patterns — ask for validation explicitly in your prompt. For phone verification flows, V0 generates multi-step forms well. A two-step component where step one collects the phone number and step two collects the OTP is a common pattern that V0 handles with React state management. The component transitions between steps based on API response success. The component should handle three states clearly in the UI: loading (while the API request is in flight, the button should show a spinner and be disabled to prevent double-submits), success (a confirmation message or progress to the next step), and error (a human-readable error message if the API call fails). V0 is good at generating these states when you describe them explicitly in your prompt. Review the generated fetch call to ensure it sends the correct content type header and body format. The Sinch SMS endpoint expects a JSON body, so the fetch should include 'Content-Type': 'application/json' and JSON.stringify the request body.

Create the server-side Next.js API route that receives requests from your V0 component and calls the Sinch SMS API. The Sinch SMS REST API endpoint is https://us.sms.api.sinch.com/xms/v1/{servicePlanId}/batches — the us subdomain sends from US numbers; use eu for European numbers. Authentication uses HTTP Basic Auth with your Service Plan ID as the username and API Token as the password. The request body is JSON with four fields: from (your Sinch virtual number), to (array of recipient phone numbers), body (the message text), and optionally delivery_report (set to 'full' to receive delivery status callbacks). Phone numbers must be in E.164 format: a plus sign followed by the country code and number, no spaces or dashes. For example, +12125551234 for a US number. This is important to validate before calling the API — Sinch rejects non-E.164 numbers. You can add basic validation in your API route to return a clear error message rather than forwarding an invalid number to Sinch and getting a confusing 400 response. The Sinch API responds with a batch object containing a message ID, status, and the list of recipients. The status will be 'Delivering' or 'Delivered' immediately — actual delivery is asynchronous. If you need confirmed delivery receipts, configure a delivery_report webhook URL in your request — Sinch will POST to that URL when the message status changes. For most notification use cases, checking the initial 201 response and treating 'Delivering' as success is sufficient. Create the file at app/api/sinch/route.ts in your project. The route exports an async POST function that reads the recipient phone number and message body from the request, validates them, and calls the Sinch API with your credentials from environment variables.

1import { NextRequest, NextResponse } from 'next/server';
2
3function validateE164(phone: string): boolean {
4  return /^\+[1-9]\d{6,14}$/.test(phone);
5}
6
7export async function POST(request: NextRequest) {
8  try {
9    const { to, message } = await request.json();
10
11    if (!to || !message) {
12      return NextResponse.json(
13        { error: 'Both to and message fields are required' },
14        { status: 400 }
15      );
16    }
17
18    if (!validateE164(to)) {
19      return NextResponse.json(
20        { error: 'Phone number must be in E.164 format (e.g., +12125551234)' },
21        { status: 400 }
22      );
23    }
24
25    if (message.length > 1600) {
26      return NextResponse.json(
27        { error: 'Message exceeds maximum length' },
28        { status: 400 }
29      );
30    }
31
32    const servicePlanId = process.env.SINCH_SERVICE_PLAN_ID!;
33    const apiToken = process.env.SINCH_API_TOKEN!;
34    const fromNumber = process.env.SINCH_FROM_NUMBER!;
35
36    const credentials = Buffer.from(`${servicePlanId}:${apiToken}`).toString('base64');
37
38    const response = await fetch(
39      `https://us.sms.api.sinch.com/xms/v1/${servicePlanId}/batches`,
40      {
41        method: 'POST',
42        headers: {
43          'Authorization': `Basic ${credentials}`,
44          'Content-Type': 'application/json',
45        },
46        body: JSON.stringify({
47          from: fromNumber,
48          to: [to],
49          body: message,
50          delivery_report: 'none',
51        }),
52      }
53    );
54
55    const data = await response.json();
56
57    if (!response.ok) {
58      console.error('Sinch API error:', data);
59      return NextResponse.json(
60        { error: data.text || 'Failed to send SMS' },
61        { status: response.status }
62      );
63    }
64
65    return NextResponse.json({
66      success: true,
67      messageId: data.id,
68      status: data.status,
69    });
70  } catch (error) {
71    console.error('Sinch route error:', error);
72    return NextResponse.json({ error: 'Internal server error' }, { status: 500 });
73  }
74}

Your API route reads three environment variables from Vercel: SINCH_SERVICE_PLAN_ID, SINCH_API_TOKEN, and SINCH_FROM_NUMBER. These must be added to Vercel's environment settings so your serverless function can access them at runtime. Go to your Vercel Dashboard and open your project. Click Settings at the top, then Environment Variables in the left sidebar. Add the following three variables: SINCH_SERVICE_PLAN_ID: This is the long alphanumeric identifier from your Sinch Customer Dashboard under SMS → REST API. It looks like a UUID with dashes. This is used both as the URL path segment in the API endpoint and as the Basic Auth username. SINCH_API_TOKEN: This is the secret API token shown alongside your Service Plan ID in the Sinch Dashboard. This is sensitive — treat it like a password. Never add a NEXT_PUBLIC_ prefix; this variable must stay server-side only. SINCH_FROM_NUMBER: This is the virtual phone number you provisioned in Sinch, in E.164 format (for example, +12025551234 for a US number). This is not secret but keeping it in an environment variable makes it easy to change without redeploying code. Set all three variables to apply to Production, Preview, and Development environments. After saving, trigger a redeployment by pushing a commit to your GitHub repository. For local development, add these same variables to your .env.local file in the project root so the API route works with Next.js dev server.

1# .env.local (local development only)
2SINCH_SERVICE_PLAN_ID=your-service-plan-id-here
3SINCH_API_TOKEN=your-api-token-here
4SINCH_FROM_NUMBER=+12025551234

With all pieces in place, test the integration end-to-end before promoting to production. Push your code changes to GitHub to trigger a Vercel deployment, then navigate to your SMS form page. During Sinch's free trial, you can only send to verified phone numbers. If you have not already, add your own mobile number as a test recipient in the Sinch Dashboard under SMS → Test Numbers. Enter your number in E.164 format and Sinch will send a verification SMS to confirm it. Once verified, use your V0-generated form to send a test SMS to your own number. Enter the phone number in E.164 format (including the country code — this is the most common mistake) and a short test message. Click Submit and watch the loading state — the request should complete within one to two seconds. You should receive the SMS on your phone within seconds. If the form submits but no SMS arrives, check three things: your Vercel function logs for API errors (Vercel Dashboard → project → Functions → Logs), the Sinch Dashboard under SMS → Logs to see if the batch was created, and your phone number format (it must start with + and include the country code). Sinch's Dashboard shows real-time message status including delivery confirmation. For production use, there are a few additional steps. First, upgrade your Sinch account from trial to paid to remove the test-number restriction and increase sending volume. Second, if you are sending to US numbers, Sinch requires campaign registration under the 10DLC (10 Digit Long Code) system — register your messaging use case in the Sinch Dashboard to avoid carrier filtering. For complex notification workflows involving delivery tracking, user opt-outs, and high-volume sends, RapidDev's team can help you set up the full Sinch integration including webhook handling for delivery receipts.