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UUID Use Case

UUID Nonce

A nonce is a value used only once. A v4 UUID is a convenient, collision-free nonce for protocol handshakes and inline script allow-lists.

One-timeReplay protectionv4

Version

How many

Uppercase Hyphens Braces { }

Result

Generated locally with the Web Crypto API — nothing leaves your browser.

What Is UUID Nonce?

Protocols use a nonce so an eavesdropper cannot replay an old message — each exchange demands a fresh value.
In Content-Security-Policy, a per-response UUID nonce lets you whitelist exactly one inline script block.

How to generate

Generate a fresh v4 UUID for every exchange or response.
Include it in the signed message or CSP header.
Reject any message whose nonce was seen before.

Use Cases

OAuth / PKCE state values.
CSP script nonces.
Challenge-response auth.

Code Examples

JavaScript

const nonce = crypto.randomUUID();
res.setHeader('Content-Security-Policy', `script-src 'nonce-${nonce}'`);

Frequently Asked Questions

Nonce vs CSRF token?

Both are random one-time values; a nonce is the general crypto term, CSRF tokens are a specific use for form protection.

Must a nonce be a UUID?

No, but a v4 UUID is a handy, guaranteed-unique source of randomness.

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