Legacy Runner sunset

Frequently Asked Questions

The Unified Runner replaces the legacy implementation for executing Chrome runs in the cloud. By default, ad hoc and plan runs will use the Unified Runner. For a limited period of time, existing accounts will have the option to use either the Unified Runner or the Legacy Runner for Chrome.

During this time, we encourage all existing customers to migrate any plans on the Legacy Runner to the Unified Runner, which can be accomplished easily by following these steps. Once this transition period ends, the Legacy Runner for Chrome will be formally retired.



Trial users and customers who joined after March 21, 2022 do not have access to the Legacy Runner for Chrome.

Timeline for sunsetting the Legacy Runner for Chrome

  • March 21, 2022: Extended support
  • October 28, 2022: End-of-support
  • February 1, 2023: End-of-life

Extended support

During the "extended support" phase, the existing functionality of the Legacy Runner for Chrome is maintained. However, new features may only be available on the Unified Runner. Bugs reported for the Legacy Runner are addressed on a case-by-case basis.


During the end-of-support phase, no further changes will be made to the Legacy Runner from Chrome, including non-critical security updates, non-security updates, and bug fixes. Bug reports for the Legacy Runner will only be considered if they are impacting testing on non-Chrome browsers (Firefox, Safari, and Internet Explorer).


During the end-of-life stage, the Legacy Chrome Runner will be formally retired. All test executions for Chrome will occur on the Unified Runner. Any existing plans using the Legacy Chrome Runner will be automatically migrated to the Unified Runner.


Legacy Runner sunset

What does it mean for the Legacy Runner to be retired?
Once the Legacy Runner is retired, all test runs on Chrome will occur on the Unified Runner. The Legacy Runner will no longer be available for use.

Why is the Legacy Runner being sunset?
The Unified Runner is the next generation of automated testing with mabl, providing a more reliable, consistent, and performant experience. The Legacy Runner will be retired as the Unified Runner was built to replace it.

When will the Legacy Runner be fully sunset?
We will fully retire the Legacy Runner on February 1st, 2023.

Can I still use the Legacy Runner?
Yes, up until the end-of-life date, the Legacy Runner will be available for all accounts created before March 21, 2022. However, there are some newer features we do not support in the Legacy Runner, including Intelligent Wait.

The Unified Runner

What improvements can I expect from the Unified Runner?
The Unified Runner is the next generation of the mabl testing service, bringing the same framework used in the mabl Desktop App and CLI to the cloud. By unifying our test execution logic, the new test runner provides consistent test results across all execution methods. This runner also offers considerable speed improvements, reducing cloud test execution time by 25%, on average.

Additionally, the Unified Runner introduces a new level of machine learning to mabl’s test automation platform: Intelligent Wait. With every run in the cloud, mabl collects timing information for each step to determine the expected wait before executing an action. This prevents test steps from executing before the application is in the correct state. These intelligent waits apply to test executions locally and in the cloud, allowing mabl to confidently test at the highest speed best suitable for the application under test.

Migrating to the Unified Runner

How can I migrate existing plans on the Legacy Runner to the Unified Runner?
Existing plans created with the Legacy Runner can be easily migrated to the Unified runner by following these steps.

What happens if I don't migrate my tests to the Unified Runner by the sunset date?
If existing plans on the Legacy Runner are not manually migrated to the Unified Runner, they will automatically migrate on February 1, 2023.

What areas of testing does this affect?
This will only impact runs in the cloud. Local test runs and Trainer replay already use the Unified Runner and will not change.

What should I look out for when migrating to the Unified Runner?
There are a few key things to note about the Unified Runner:

  • Only Chrome and Edge are supported at this time. More browsers to follow later.
  • Visual smoke tests are unsupported at this time and will use the Legacy Runner.
  • Link crawler tests are unsupported at this time and will use the Legacy Runner.
  • Additional information on small behavioral differences can be found here.

What if I run into issues while migrating tests from the Legacy Runner to the Unified Runner?
Tests that ran successfully in the cloud on the Legacy Runner should continue to work in the Unified Runner. If something does not work as expected, please reach out to our support team with additional information.

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