---
title: "__UUID"
description: "JMeter __UUID function reference: syntax, parameters, and practical examples for parameterizing test plans with dynamic values."
url: https://docs.jmeter.ai/functions/uuid/
lastUpdated: 2026-10-01
source: docs.jmeter.ai
---

# __UUID

*Also documented in context in the [full Functions and Variables reference](/user-manual/functions/#__UUID).*

**TL;DR:** `__UUID` returns a random RFC 4122 UUID (v4) — the standard choice for a genuinely unique identifier per request (idempotency keys, correlation IDs, unique record creation) where a sequential counter would collide across parallel test runs.

The UUID function returns a pseudo random type 4 Universally Unique IDentifier (UUID).

Examples:

```bash
\${__UUID()}
```

will return UUIDs with this format : `c69e0dd1-ac6b-4f2b-8d59-5d4e8743eecd`

### Example

```plaintext
${__UUID()}   → e.g. 8f14e45f-ceea-467e-b7d1-9d1946a4c8b1
```

Common use: an `Idempotency-Key` header on a payment/order-creation [HTTP Request](/components/http-request/), or a unique record name so repeated test runs don’t collide on a unique-constraint. For sequential (not random) unique values, see [__counter](/functions/counter/).

## Related

- [Functions and Variables Guide](/topics/functions-and-variables/)
- [Regex Extractor Builder](/tools/regex-tester/)
- [Correlation & Dynamic Values](/topics/correlation-dynamic-values/)
- [Full Functions Reference](/user-manual/functions/)
- [Component Reference](/user-manual/component-reference/)