Edit running virtual users

While a test runs, you can change the number of virtual users (VUs) in each population without stopping the test. This lets you change the test load in real time, so you don't have to edit and restart the test.

You can edit VUs only while the test runs. After the test finishes, this action is no longer available.

To change the number of virtual users during a test run, follow these steps:

  1. Go to the Results > Running VUs tab of the running test:

    • Select Edit running VUs at the top of the page to edit all populations at once.

    • Select one or more populations from the list in the Populations tab to edit specific populations.

  2. For each population, select – to stop running an amount of VUs or select + to add more VUs.

  3. If you stop running VUs in a population, select the stop policy:

    • Apply the stop policy from the test scenario: NeoLoad stops the VUs as defined in the population's stop policy.

    • Stop immediately: NeoLoad stops the VUs right away.

  4. Select Send request.

The edit isn't applied immediately. NeoLoad first sends a request to check if it's valid for the current state of the test: for example, if the population you want to edit is still running. To see the results of the request, check the VUs change log tab.

You need to have the Controller version 2026.2 or above to edit running VUs.

VUs and VUH consumption

When you add VUs, NeoLoad uses test resources based on how the test started:

  • Test started with VUs only: NeoLoad adds VUs up to the VUs left in the lease. You can't go above the number of VUs in the lease.

  • Test started with VUs and VUH: NeoLoad first uses the VUs left in the lease, then consumes Virtual User Hour (VUH) for the rest. NeoLoad calculates the exact VUH usage after the test ends.

VUs distribution and lease limit

If the added VUs reach the lease limit and you don't have available VUH, it will affect the VUs distribution initially configured in the test. For example, a ramp up scenario distributes 50 VUs at startup and 50 more after 30 minutes. It takes a 100-VU lease. If you add 5 VUs mid-test, leaving 45 in the lease, NeoLoad can only add 45 remaining VUs at the 30-minute step.

To avoid this, allocate extra VUs to the lease when you start the test. That way, you have resources to spare if you need to go above the VUs planned in your scenario.

What's next

Learn how to Analyze results to monitor the impact of your changes on the test.