next.config.js

// https://securityheaders.com
const ContentSecurityPolicy = `
  default-src 'self';
  script-src 'self' 'unsafe-eval' 'unsafe-inline';
  child-src 'none';
  style-src 'self' 'unsafe-inline';
  img-src * blob: data:;
  media-src 'none';
  connect-src *;
  font-src 'self';
`;

const securityHeaders = [
	// https://developer.mozilla.org/en-US/docs/Web/HTTP/CSP
	{
		key: 'Content-Security-Policy',
		value: ContentSecurityPolicy.replace(/\n/g, ''),
	},
	// https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Referrer-Policy
	{
		key: 'Referrer-Policy',
		value: 'origin-when-cross-origin',
	},
	// https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Frame-Options
	{
		key: 'X-Frame-Options',
		value: 'DENY',
	},
	// https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Content-Type-Options
	{
		key: 'X-Content-Type-Options',
		value: 'nosniff',
	},
	// https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-DNS-Prefetch-Control
	{
		key: 'X-DNS-Prefetch-Control',
		value: 'on',
	},
	// https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Strict-Transport-Security
	{
		key: 'Strict-Transport-Security',
		value: 'max-age=31536000; includeSubDomains; preload',
	},
];

const withBundleAnalyzer = require('@next/bundle-analyzer')({
	enabled: process.env.ANALYZE === 'true',
});

module.exports = withBundleAnalyzer({
	headers: () => [
		{
			source: '/',
			headers: securityHeaders,
		},
		{
			source: '/:path*',
			headers: securityHeaders,
		},
	],
});