A CSP nonce is a one-time value used in a Content Security Policy to allow only specific trusted inline scripts or styles to execute. It matters because strict browser content policies often need a safe way to allow intended inline code without opening the door broadly.
What is CSP Nonce?
The server generates a fresh random nonce and includes it both in the CSP header and on the allowed inline script or style elements. The browser then runs only the tagged content, helping reduce the chance that injected inline content will execute.
What CSP Nonce Commonly Supports
Common uses include safer inline script handling, modern CSP deployment, controlled exception management, and reduction of risky allowlists such as unsafe-inline.
CSP Nonce vs. Broad Inline Script Allowance
Broad inline allowance weakens CSP substantially. A nonce narrows execution to specifically approved inline content for that response.
Frequently Asked Questions
Why is a CSP nonce useful?
Because it provides a safer pattern for necessary inline content without allowing arbitrary inline execution.
Should a nonce be reused?
No. It should be unique per response or context to preserve its security value.
Related Cybersecurity Terms
- Content Security Policy (CSP)
- Browser Security
- Subresource Integrity (SRI)
- Secure Software Development Lifecycle (SSDLC)
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