CSP Browser Support and Compatibility

Understanding browser support is crucial for successful CSP implementation. While modern browsers have excellent CSP support, variations exist in feature implementation and older browser handling.

Current browser support for CSP Level 2 and Level 3 features:

// Feature detection for CSP support
function detectCSPSupport() {
    const testPolicy = "default-src 'none'";
    
    // Check for CSP support via meta tag
    const meta = document.createElement('meta');
    meta.httpEquiv = 'Content-Security-Policy';
    meta.content = testPolicy;
    
    // Test if the browser respects CSP
    try {
        document.head.appendChild(meta);
        
        // Attempt to execute inline script (should fail with CSP)
        const result = eval('true');
        
        // If we reach here, CSP is not working
        document.head.removeChild(meta);
        return false;
    } catch (e) {
        // CSP blocked the eval, support confirmed
        document.head.removeChild(meta);
        return true;
    }
}

Browser compatibility considerations:

Chrome/Edge: Full support for CSP3 features including 'strict-dynamic'
Firefox: Comprehensive CSP support with some experimental features
Safari: Good CSP2 support, gradual adoption of CSP3 features
Internet Explorer: Limited to CSP1 with the X-Content-Security-Policy header