Security Headers Builder

Quick Solution

Select the security directives you need—such as Content-Security-Policy (CSP), Strict-Transport-Security (HSTS), or X-Frame-Options—and instantly copy the properly formatted configuration block for your web server (Nginx, Apache, Express, etc.).

When Should I Use This?

Generating strict HTTP security headers is a fundamental step in hardening any web application or infrastructure deployment.

• Passing rigorous security audits for enterprise compliance (such as PCI-DSS or SOC2).
• Hardening new web applications against Cross-Site Scripting (XSS) and clickjacking vulnerabilities.
• Fixing Lighthouse security warnings or Mozilla Observatory scan failures on your production domains.

Troubleshooting

Issue: CSP is blocking inline scripts (Refused to execute inline script)
Fix: Your Content-Security-Policy is doing its job by blocking dangerous <script> tags. To fix your application, either move your JavaScript into external files, or add a cryptographic nonce or hash to your script-src directive.

Issue: HSTS locking out HTTP-only subdomains
Fix: If you enabled includeSubDomains in your HSTS header, all subdomains must support HTTPS. If an internal subdomain only supports HTTP, the browser will refuse to connect. Remove includeSubDomains until all your subdomains have valid SSL/TLS certificates installed.

Understanding HTTP Security Headers in Modern Web Development

HTTP security headers are one of the most effective and straightforward ways to harden a web application. By simply sending the right headers in your server's HTTP responses, you can instruct the browser to enforce security policies that mitigate entire classes of vulnerabilities. These include Cross-Site Scripting (XSS), clickjacking, protocol downgrade attacks, and malicious data injections.

When a browser requests a web page, the web server responds with the HTML content and a set of HTTP response headers. Security headers act as a set of rules that the browser must follow when rendering the page or executing scripts. If you are experiencing cross-origin API issues, make sure to also properly configure your server using our CORS Header Generator.

How It Works: The Security Headers Builder

Configuring these headers correctly can be incredibly tedious and error-prone. A single syntax error in a Content-Security-Policy can break your site's core functionality by blocking legitimate scripts, web fonts, or stylesheets.

Our Security Headers Builder provides a safe, visual way to construct these headers. Here is exactly how the generation process works:

1. Interactive Selection: You visually toggle the exact security directives you need, such as HSTS preloading or CSP script-src domains.
2. Syntax Validation: The tool automatically formats the values, ensuring that strings are properly quoted and directives are separated by semicolons according to the RFC specifications.
3. Server Translation: The builder converts the abstract headers into the exact syntax required for your specific web server, whether you are writing an Nginx add_header block, an Apache Header set directive, or Express.js middleware.
4. Instant Generation: The configuration snippet is generated in real-time, ready to be pasted directly into your server configuration. If you are configuring Nginx from scratch, you can pair this with our Nginx Config Generator.

Deep Dive into Critical Security Headers

Content-Security-Policy (CSP)

The Content-Security-Policy header is arguably the most powerful security mechanism available in modern browsers. It operates on a simple principle of "default deny." Instead of trying to filter out malicious scripts, a CSP tells the browser exactly which domains are explicitly allowed to load resources like scripts, styles, images, and fonts. If a script comes from an unauthorized source, or if an attacker attempts to inject inline JavaScript into the page, the browser will simply refuse to run it, neutralizing XSS attacks immediately.

Strict-Transport-Security (HSTS)

HTTP Strict Transport Security (HSTS) is crucial for securing the communication channel between the user and the server. It informs browsers that the site should only ever be accessed using HTTPS. This prevents protocol downgrade attacks, where a man-in-the-middle attacker attempts to strip the SSL encryption and force the connection over plain HTTP. By setting the includeSubDomains and preload directives, you ensure maximum protection across your entire domain structure.

X-Frame-Options and Frame-Ancestors

Clickjacking attacks occur when a malicious site embeds your web application inside a transparent iframe, tricking the user into clicking buttons on your site without their knowledge. The older X-Frame-Options header (using DENY or SAMEORIGIN) prevents your site from being framed. The modern equivalent is the CSP frame-ancestors directive, which provides more granular control by allowing you to specify the exact domains that are permitted to embed your site. We recommend deploying both for maximum compatibility.

Cross-Origin Opener & Embedder Policies (COOP & COEP)

For applications that require high-performance features like SharedArrayBuffer, browsers demand that your site is "cross-origin isolated." This prevents sophisticated side-channel attacks like Spectre. By configuring Cross-Origin-Opener-Policy: same-origin and Cross-Origin-Embedder-Policy: require-corp, you create a secure, isolated environment for your application to execute memory-intensive operations safely.

Browser Compatibility

Understanding how different browsers handle security headers is essential for maintaining both security and usability across your user base:

• Google Chrome & Chromium (Edge, Brave, Opera): Excellent support for all modern headers, including strict COOP/COEP enforcement and all CSP Level 3 directives.
• Mozilla Firefox: Full support for CSP, HSTS, and X-Frame-Options. Firefox also strictly enforces the Permissions-Policy for embedded iframes.
• Apple Safari (WebKit): Supports the vast majority of security headers. However, Safari sometimes lags in implementing the newest CSP Level 3 features (like strict-dynamic). The generated headers include fallback mechanisms to ensure legacy support.
• Legacy Browsers: Browsers that do not understand a specific security header will simply ignore it. This means implementing security headers acts as a progressive enhancement; it improves security for modern browsers without breaking the site for older ones.

Why Privacy Matters When Generating Security Headers

When you are building a complex Content-Security-Policy, you are essentially documenting the architecture and trusted third-party dependencies of your application. You are listing your payment gateways, analytics providers, font CDNs, and API endpoints. You should not have to send this sensitive architectural blueprint to a third-party server just to generate a configuration block.

This tool is 100% private — your configurations and architecture maps never leave your browser.

Our Security Headers Builder runs entirely using local JavaScript in your browser's memory. Your configuration choices and the generated Nginx, Apache, or Express blocks are never transmitted over the network, logged, or stored in any external database. You get a robust, production-ready security configuration instantly, securely, and privately.