__threadNum

Also documented in context in the full Functions and Variables reference.

TL;DR: __threadNum returns the current thread’s number (1, 2, 3, …) within its Thread Group — useful for deriving per-thread test data (e.g. user${__threadNum}) without a CSV file.

The thread number function simply returns the number of the thread currently being executed. These numbers are only locally unique with respect to their ThreadGroup, meaning thread #1 in one threadgroup is indistinguishable from thread #1 in another threadgroup, from the point of view of this function.

Note

The function returns a number between one and the max number of running threads. Note that if you’re using JSR223 code with JMeterContext object (ctx variable), the below code returns a number between zero and (max number of running threads minus one)

ctx.getThreadNum()

There are no arguments for this function.

Usage Example:

\${__threadNum}

returns a number between 1 and the max number of running threads configured in the containing Thread Group

Note

This function does not work in any Configuration elements (e.g. User Defined Variables) as these are run from a separate thread. Nor does it make sense to use it on the Test Plan.

Example

${__threadNum}   → e.g. 3 for the third thread started

Combine with __threadGroupName when a test plan has multiple Thread Groups and per-group-scoped IDs are needed. For genuinely unique values across a distributed run (multiple injectors), prefer __UUID — thread numbers restart from 1 on every injector.

Related

• Functions and Variables Guide
• Regex Extractor Builder
• Thread Groups & Workload Modeling
• Full Functions Reference
• Component Reference