next.config.js

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

// You might need to insert additional domains in script-src if you are using external services
const ContentSecurityPolicy = `
  default-src 'self';
  script-src 'self' 'unsafe-eval' 'unsafe-inline' plausible.io;
  style-src 'self' 'unsafe-inline';
  img-src * blob: data:;
  media-src *.s3.amazonaws.com;
  connect-src *;
  font-src 'self';
  frame-src ;
`;

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: "strict-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"
  },
  // https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Feature-Policy
  {
    key: "Permissions-Policy",
    value: "camera=(), microphone=(), geolocation=()"
  }
];

/**
 * @type {import('next/dist/next-server/server/config').NextConfig}
 **/
module.exports = () => {
  const plugins = [withBundleAnalyzer];
  return plugins.reduce((acc, next) => next(acc), {
    reactStrictMode: true,
    pageExtensions: ["ts", "tsx", "js", "jsx", "md", "mdx"],
    eslint: {
      dirs: ["app", "components"]
    },
    images: {
      domains: []
    },
    compiler: {
      // removeConsole: true
    },
    async headers() {
      return [
        {
          source: "/(.*)",
          headers: securityHeaders
        }
      ];
    }
  });
};