How to Integrate Let's Encrypt with V0

Before configuring anything, it helps to understand what Vercel does automatically so you know you do not need to do it manually. When you deploy a V0 app to Vercel, the deployment immediately gets HTTPS via a shared certificate on *.vercel.app. When you add a custom domain, Vercel initiates the Let's Encrypt certificate issuance process using the ACME protocol. Specifically, Vercel uses the ACME HTTP-01 challenge: it temporarily serves a specific file at /.well-known/acme-challenge/ on your domain to prove to Let's Encrypt that Vercel controls that domain. Let's Encrypt verifies the file exists at that URL, then issues a 90-day certificate. Vercel renews the certificate automatically before it expires — you never need to think about 90-day renewals. All of this happens without any action from you beyond setting the correct DNS records. The certificate covers your exact domain and, on Vercel Pro plans, also covers the www subdomain if you configure it. Vercel uses a certificate authority called Let's Encrypt for standard domains, but may use other CAs (like ZeroSSL) depending on rate limits and infrastructure decisions — you do not control this choice. The key practical implication: if your V0 app is deployed to Vercel and you use a custom domain, your SSL is handled. The scenarios where you might manually interact with Let's Encrypt are: (1) you have a companion service running on a different server that your V0 app communicates with, (2) you need a wildcard certificate for *.yourapp.com for dynamic subdomains that Vercel does not support on your plan, or (3) you are evaluating moving off Vercel and want to understand the certificate management implications. For the vast majority of V0 users, this step is the end of the SSL configuration journey — add your domain in Vercel Dashboard and you are done.

When you add a custom domain to your Vercel project, Vercel begins the Let's Encrypt certificate provisioning process automatically. Here is the exact sequence to follow. In your Vercel Dashboard, open your project and click the Settings tab, then click Domains in the left sidebar. Click the Add Domain button and enter your custom domain (e.g., myapp.com). Vercel will show you DNS configuration instructions — typically one of two patterns: a CNAME record pointing to cname.vercel-dns.com, or an A record pointing to Vercel's IP address (76.76.21.21) for apex domains. Log into your domain registrar's control panel and add the DNS record Vercel specifies. DNS propagation typically takes 5-30 minutes, though it can take up to 48 hours in rare cases. During this time, Vercel's dashboard shows the domain status as 'Pending' or 'Invalid Configuration' until the DNS change propagates. Once Vercel detects the correct DNS configuration, it automatically requests a certificate from Let's Encrypt. This usually completes within 2-3 minutes. The Vercel Domains panel shows a green checkmark and 'Valid Configuration' when the certificate is successfully issued and the domain is live. For the www subdomain, add www.myapp.com as a second domain in Vercel and set up a redirect from www to your apex domain (or vice versa, depending on your preference). Vercel provisions a separate certificate for each domain variant. Note that on Vercel's Hobby plan, you can add up to 50 domains; the Pro plan supports unlimited domains with wildcard options. One subtlety with apex domains (the root domain without www): some DNS providers use ALIAS, ANAME, or CNAME flattening records for apex domains instead of standard CNAME records, because standard DNS does not allow CNAME at the apex. Consult your domain registrar's documentation for the correct record type. Cloudflare, Namecheap, and most modern registrars support the necessary record types.

Even with Vercel's automatic SSL, your V0 app benefits from explicitly enforcing HTTPS redirects and adding security headers. HTTP Strict Transport Security (HSTS) tells browsers to always use HTTPS for your domain, even if a user types http:// — the browser converts it to HTTPS locally before making a request. This prevents SSL stripping attacks and improves user experience. In Next.js App Router, you can add security headers in next.config.ts using the headers() configuration function. These headers apply to all responses from your Vercel deployment. The most important headers for HTTPS enforcement are: Strict-Transport-Security (HSTS): tells browsers to use HTTPS exclusively for a specified duration. A max-age of 31536000 (1 year) is standard for production. The includeSubDomains directive extends this to all subdomains. The preload flag submits your domain to browser preload lists — only add preload when you are sure your entire domain hierarchy supports HTTPS. X-Content-Type-Options: set to 'nosniff' to prevent browsers from interpreting files as a different MIME type than declared. This prevents MIME confusion attacks. X-Frame-Options: set to 'SAMEORIGIN' to prevent clickjacking by disallowing your pages from being embedded in iframes on other domains. For the HTTP to HTTPS redirect itself, Vercel automatically redirects HTTP to HTTPS for all deployments at the infrastructure level — you do not need to handle this in your Next.js middleware. However, if you see cases where HTTP requests are not redirecting (particularly for API routes), adding an explicit middleware redirect gives you a safety net. Vercel also supports Next.js redirects configuration in next.config.ts for managing URL redirects independent of SSL — for example, redirecting www to non-www or handling old URL patterns. These are application-level redirects, separate from the infrastructure-level HTTPS redirect Vercel handles automatically.

1// next.config.ts
2import type { NextConfig } from 'next';
3
4const nextConfig: NextConfig = {
5  async headers() {
6    return [
7      {
8        // Apply security headers to all routes
9        source: '/(.*)',
10        headers: [
11          {
12            key: 'Strict-Transport-Security',
13            value: 'max-age=31536000; includeSubDomains',
14          },
15          {
16            key: 'X-Content-Type-Options',
17            value: 'nosniff',
18          },
19          {
20            key: 'X-Frame-Options',
21            value: 'SAMEORIGIN',
22          },
23          {
24            key: 'Referrer-Policy',
25            value: 'strict-origin-when-cross-origin',
26          },
27          {
28            key: 'Permissions-Policy',
29            value: 'camera=(), microphone=(), geolocation=()',
30          },
31        ],
32      },
33    ];
34  },
35};
36
37export default nextConfig;

If your V0 app's SSL certificate is not working correctly after adding a custom domain, follow this diagnostic sequence to identify and fix the issue. First, check the Vercel Dashboard status for your domain: Settings → Domains. Vercel shows specific error messages when certificate provisioning fails. Common status messages include 'Invalid Configuration' (DNS not pointing to Vercel), 'Certificate Pending' (DNS is correct but certificate is still being issued), and 'Error' (certificate issuance failed, usually due to Let's Encrypt rate limits or DNS propagation issues). Let's Encrypt rate limits are a real concern: Let's Encrypt limits certificate issuance to 50 certificates per registered domain per week and 5 failures per account per hour. If you or Vercel has hit rate limits (common in active development with many domain reconfigurations), certificate issuance will fail silently or with a rate limit error. The solution is to wait until the rate limit window resets (typically within hours for the failures limit, up to a week for the domain limit). For DNS configuration issues, the most common mistake is setting a CNAME record for an apex domain (yourdomain.com without www). Standard DNS does not allow CNAME records at the apex — use an A record pointing to 76.76.21.21 instead, or if your DNS provider supports it, use ALIAS/ANAME records. Using a CNAME for www.yourdomain.com is correct and recommended. If your custom domain shows 'Your connection is not private' in the browser even though Vercel shows 'Valid Configuration', clear your browser's HSTS cache for that domain: in Chrome, go to chrome://net-internals/#hsts, enter your domain under 'Delete domain security policies', and click Delete. Then test in a fresh incognito window. For expired certificate warnings, Vercel's automatic renewal should prevent this, but if it occurs, go to Vercel Dashboard → your project → Settings → Domains, remove the domain, and re-add it to trigger a fresh certificate issuance.

If your V0 app communicates with a backend service you host yourself (a Node.js WebSocket server, a Python API, a database proxy, etc.), that companion service also needs HTTPS with a valid SSL certificate for secure communication. Vercel cannot manage certificates for servers you own — that is where manual Let's Encrypt configuration comes in. For a VPS or dedicated server running Ubuntu or Debian, the recommended approach is Certbot from the Electronic Frontier Foundation. Certbot automates certificate issuance and sets up automatic renewal via a cron job or systemd timer. The commands look like: sudo certbot --nginx -d yourapi.yourdomain.com for an Nginx server, or sudo certbot --apache for Apache. However, if you are running a Node.js API server without a web server in front, you can use the acme-client npm package to implement the ACME protocol directly in Node.js without installing system tools. The acme-client package supports both HTTP-01 and DNS-01 challenges and can store certificates in any location your Node.js app can write to. For this scenario, your V0 Next.js app calls your self-hosted API using HTTPS with the Let's Encrypt certificate. Store the API's base URL as an environment variable in Vercel (e.g., API_BASE_URL=https://api.yourdomain.com) and reference it in your Next.js API routes with process.env.API_BASE_URL. Since both Vercel and Let's Encrypt issue trusted certificates, the HTTPS connection between them is valid without any additional configuration. For development environments, avoid self-signed certificates if possible — they require disabling certificate verification in fetch calls (NODE_TLS_REJECT_UNAUTHORIZED=0), which is a bad habit that can leak into production. Instead, use tools like mkcert to generate locally trusted development certificates or proxy all requests through your Vercel deployment URL during development.

1// app/api/external/route.ts — calling a self-hosted service with HTTPS
2import { NextRequest, NextResponse } from 'next/server';
3
4const API_BASE_URL = process.env.API_BASE_URL;
5
6export async function GET(request: NextRequest) {
7  if (!API_BASE_URL) {
8    return NextResponse.json(
9      { error: 'API_BASE_URL not configured' },
10      { status: 500 }
11    );
12  }
13
14  // Calls your self-hosted service over HTTPS
15  // Let's Encrypt cert on the API server makes this connection trusted
16  const response = await fetch(`${API_BASE_URL}/your-endpoint`, {
17    headers: {
18      // Auth between V0 app and your API
19      Authorization: `Bearer ${process.env.API_SECRET_KEY}`,
20    },
21  });
22
23  if (!response.ok) {
24    return NextResponse.json(
25      { error: 'External API call failed' },
26      { status: response.status }
27    );
28  }
29
30  const data = await response.json();
31  return NextResponse.json(data);
32}