> OctoPerf load testing - Variable documentation page. To configure predefined variables (Constant, Random or CSV), in one place.
Source: https://api.octoperf.com/doc/design/edit-virtual-user/configuration/variables/
# Variables
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The variable page lets you configure, **variables to use in your virtual users**.
These variables will be **shared across the project**, meaning they are available to any virtual user in this project.
Because of that you should **pay extra care when making changes** since they can have an impact on several virtual users.
## Variables list
The variables page uses a layout with the list on the left and edition on the right. The list features all the usual possibilities as described in the [dedicated section about lists](https://api.octoperf.com/doc/navigation/#lists).
When a CSV variable has a problem, such as a missing file or a conflict with another variable, the list shows a status column: see [Where the problems show](https://api.octoperf.com/doc/design/edit-virtual-user/configuration/variables/csv-validation/#where-the-problems-show) and how to fix each problem in the [CSV Variable Check](https://api.octoperf.com/doc/design/edit-virtual-user/configuration/variables/csv-validation/#problem-index).
### Usage
A single click inside the usage section will **copy a variable name** in order for you to use it in your virtual user. This way you do not have to manually input the **${...}** syntax.
!!! info
Variables can be used anywhere in your virtual user except in:
- Container names
- Request names
This means you can use variables inside text content like in JSR scripts ([although not recommended](https://api.octoperf.com/doc/design/edit-virtual-user/action-types/jsr223-actions/#jmeter-variables-and-functions)) or inside [raw bodies of requests](https://api.octoperf.com/doc/design/edit-virtual-user/action-types/http-actions/#raw).
Nested variables are possible but this [requires the use of a function](https://api.octoperf.com/doc/design/edit-virtual-user/functions/#__v).
## Variables types
- :material-pi: Constant Variable
---
Associate a single constant value to the variable name.
[:octicons-arrow-right-24: Reference](https://api.octoperf.com/doc/design/edit-virtual-user/configuration/variables/constant/)
- :fontawesome-solid-shuffle: Random Variable
---
Associate a single random value to the variable name.
[:octicons-arrow-right-24: Reference](https://api.octoperf.com/doc/design/edit-virtual-user/configuration/variables/random/)
- :fontawesome-solid-arrow-up-wide-short: Counter Variable
---
Increase the count inside this variable on every iteration.
[:octicons-arrow-right-24: Reference](https://api.octoperf.com/doc/design/edit-virtual-user/configuration/variables/counter/)
- :fontawesome-solid-file-csv: CSV Variable
---
Use a [CSV formatted file](http://en.wikipedia.org/wiki/Comma-separated_values) for the values of the variable.
[:octicons-arrow-right-24: Reference](https://api.octoperf.com/doc/design/edit-virtual-user/configuration/variables/csv/)
[:octicons-arrow-right-24: CSV Variable Check](https://api.octoperf.com/doc/design/edit-virtual-user/configuration/variables/csv-validation/)
- :fontawesome-solid-user-secret: Secret Variable
---
The value of this variable is not visible anymore after its creation.
[:octicons-arrow-right-24: Reference](https://api.octoperf.com/doc/design/edit-virtual-user/configuration/variables/secret/)
## Predefined variables
### JMeterThread.last_sample_ok
This variable contains **true** or **false** depending on the status of the last sample executed.
!!! example
`${JMeterThread.last_sample_ok}` after a sampler ok, returns **true**
### START.HMS
This variable contains the JMeter start time in [UTC time](https://time.is/UTC).
!!! example
`${START.HMS}` returns **122402** for a test started at 12:24:02.
### START.MS
This variable contains the JMeter start timestamp in [UTC time](https://time.is/UTC).
!!! example
`${START.MS}` returns **1631190242724** for a test started at 12:24:02 on the 9th of september 2021.
### START.YMD
This variable contains the JMeter start date in [UTC time](https://time.is/UTC).
!!! example
`${START.YMD}` returns **20210909** for a test started on the 9th of september 2021.
### TESTSTART.MS
This variable contains the test start timestamp in [UTC time](https://time.is/UTC). It differs from the JMeter start time since it measure the effective start time of the first thread.
!!! example
`${TESTSTART.MS}` returns **1631190243262**
### \_\_jmeter.U_T\_\_
This variable contains the threadgroup name followed by `virtual user number`-`iteration number`.
!!! example
`${__jmeter.U_T__}` returns **unOEv3sBYy9LOuX37AC2 1-1**