301と302リダイレクトの使い分けと設定方法

# Check redirect chain via curl
curl -L -s -o /dev/null -w "%{url_effective}\n%{http_code}\n%{redirect_url}\n" \
  https://old-domain.com/page

# Check all redirects in the chain
curl -L -v https://old-domain.com/page 2>&1 | grep -E "^< HTTP|^> GET|Location:"

# 301: permanent redirect for a single page
server {
  location = /old-page {
    return 301 /new-page;
  }
}

# 301: full domain redirect
server {
  server_name old-domain.com;
  return 301 https://new-domain.com$request_uri;
}

# 301: HTTP → HTTPS
server {
  listen 80;
  server_name example.com www.example.com;
  return 301 https://example.com$request_uri;
}

# 302: temporary redirect
server {
  location = /promo {
    return 302 /sale;
  }
}

// next.config.ts
const nextConfig = {
  async redirects() {
    return [
      // 301: permanent redirect
      {
        source: '/old-blog/:slug',
        destination: '/blog/:slug',
        permanent: true, // = 301
      },
      // 302: temporary redirect
      {
        source: '/promo',
        destination: '/sale',
        permanent: false, // = 302
      },
    ];
  },
};

export default nextConfig;