Content Security Policy (CSP) Header Builder & Validator
Build, validate, and simulate strict W3C Content Security Policy (CSP Level 3) headers to prevent Cross-Site Scripting (XSS) and clickjacking.
01. Preventing XSS and Data Injection with Content Security Policy (Level 3)
Content Security Policy (CSP) is an HTTP response header that allows site administrators to declare approved sources of content that browsers are allowed to load (scripts, stylesheets, images, fonts, frames, and WebSocket connections).
A properly configured strict CSP header mitigates Cross-Site Scripting (XSS), data exfiltration, packet sniffing, and clickjacking attacks.
Our visual builder lets you configure directives (`default-src`, `script-src`, `style-src`, `img-src`, `connect-src`, `frame-ancestors`) and outputs ready-to-use HTTP headers or HTML meta tags.
- Visual directive configuration with support for 'self', 'unsafe-inline', nonces, and hashes.
- Instant detection of insecure wildcards and dangerous directive combinations.
- Outputs for Nginx, Apache, Cloudflare, and HTML meta tags.
02. How to Build a Production CSP Header
1. Start with a restrictive baseline: `default-src 'self'`.
2. Add trusted external domains for fonts (fonts.googleapis.com) and CDNs.
3. Prevent clickjacking by setting `frame-ancestors 'none'` or `'self'`.
4. Copy the generated header string and deploy to your web server configuration.
03. Web Application Security & Cryptographic Nonce Workflow
Calculate SHA-256 script nonces and hashes for inline CSP directives with our Hash Generator, encode binary hashes to Base64 using Base64 to Hex Converter, and verify response headers alongside HTTP status codes with the HTTP Status Inspector.
Frequently Asked Questions (FAQ)
What is the difference between CSP header and meta tag?
HTTP headers support all directives including frame-ancestors and report-uri; meta tags support content directives only.
What is CSP Report-Only mode?
Content-Security-Policy-Report-Only monitors violations without blocking resources, ideal for testing.
Is this builder secure?
Yes, 100% of policy generation occurs in your browser.
How does local in-browser processing protect sensitive enterprise credentials?
All code runs inside your local browser memory. No data is ever sent to an outside server. Your keys, tokens, and code remain completely private on your device.
Can I use this tool offline or within air-gapped networks?
Yes. Once the page loads, it works fully offline. You can use it safely on airplanes, private corporate networks, and secure offline computers.
How does the builder handle complex Content Security Policies with dozens of directives?
The CSP builder serializes and validates directive syntax in real time. It supports 30+ CSP Level 3 directives and policies with hundreds of whitelist origins with instantaneous UI updates.
Are outputs formatted according to official industry standards?
Yes. All conversions follow official web and data standards. This ensures your outputs work smoothly across Linux, macOS, and Windows systems.
Is my confidential data uploaded to external servers when using Content Security Policy (CSP) Builder?
No. Core processing in Content Security Policy (CSP) Builder executes in volatile browser memory without server uploads. Inputs to local tools are not logged on remote servers; optional cloud-assisted features require user consent.
Is Content Security Policy (CSP) Builder free to use with any rate limits or paywalls?
Core tools are free to use without an account. Device memory and tool-specific safety limits apply. Optional AI and online contact services have usage limits.