Content Security Policy Builder
Generate Content-Security-Policy header from allowed resource origins
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About Content Security Policy Builder
Build a Bulletproof Content Security Policy Without the Guesswork
Cross-site scripting, data injection, and clickjacking attacks remain among the most common web security threats, and a well-crafted Content Security Policy is one of your strongest defenses. But CSP headers are notoriously tricky to write correctly. One misplaced directive can block your own scripts, break third-party integrations, or leave gaps that attackers exploit. The Content Security Policy Builder provides a visual, guided approach to constructing CSP headers that actually work.
If you've ever deployed a CSP only to find your site's fonts disappeared, your analytics stopped recording, or your embedded videos went blank, you know the frustration. This tool prevents those surprises by making every directive visible and every consequence clear before you deploy.
What a Content Security Policy Controls
A CSP tells the browser which sources of content are allowed to load on your page. It covers scripts, stylesheets, images, fonts, media, frames, form actions, base URIs, and more. Each resource type has its own directive, and the builder lets you configure each one independently.
The default-src directive sets the fallback policy for any resource type you don't explicitly configure. script-src controls where JavaScript can load from. style-src governs stylesheets. img-src handles images, font-src covers web fonts, connect-src restricts AJAX and WebSocket destinations, and frame-src determines which domains can be embedded in iframes.
Beyond source restrictions, CSP offers directives like upgrade-insecure-requests (automatically upgrades HTTP to HTTPS), block-all-mixed-content, and frame-ancestors (preventing your site from being embedded on malicious pages).
Building Your Policy Step by Step
The tool walks you through each directive category with clear explanations. Start with your default policy, then customize individual directives for resource types that need different rules. For each directive, you can specify allowed origins by domain, use keyword values like self, unsafe-inline, or unsafe-eval, or add nonce and hash-based allowlists for specific inline scripts.
As you build, the tool displays the complete CSP header in real time. It also shows warnings when you enable permissive settings like unsafe-inline for scripts, explaining the security implications and suggesting safer alternatives like nonce-based approaches.
When your policy is ready, copy the header value for direct use, or grab the meta tag version for HTML-based deployment. The tool also generates report-only variants so you can test your policy in monitoring mode before enforcing it.
Who Needs a Content Security Policy Builder?
Web developers adding CSP to existing applications face the biggest challenge because established sites often load resources from many different origins. The builder helps you inventory all required sources and construct a policy that covers them without being overly permissive.
Security engineers performing hardening reviews can use the tool to prototype tighter policies, testing different directive combinations before recommending changes to development teams.
DevOps teams managing multiple web properties benefit from the builder's ability to create and save policy templates that can be adapted for different applications within the same organization.
Frontend developers integrating third-party services such as analytics platforms, payment processors, chat widgets, and social media embeds need to know exactly which domains to whitelist for each service. The builder makes this enumeration process systematic rather than trial-and-error.
Avoiding Common CSP Mistakes
Don't start with an overly strict policy on a production site. Begin with Content-Security-Policy-Report-Only to collect violation reports without breaking functionality. The builder generates report-only headers specifically for this testing phase.
Avoid unsafe-inline and unsafe-eval for scripts whenever possible. They effectively disable CSP's protection against XSS. If you must allow inline scripts, use nonces or hashes instead.
Remember that CSP is additive within a directive but the most restrictive policy wins when multiple headers are present. The builder helps you understand these interactions.
The Content Security Policy Builder runs entirely in your browser. No server ever sees your security configuration, and there's no account required. Build, test, and deploy stronger security headers with confidence.