You can use the new_lookml_runtime parameter to override your Looker instance's default LookML runtime. The default runtime for projects on your instance is configured with the Use Legacy LookML Runtime legacy toggle:
If the Use Legacy LookML Runtime legacy feature is enabled, projects on the instance will use the legacy LookML runtime by default. LookML developers can add new_lookml_runtime: yes to a project to override the instance default and enable the new LookML runtime for the project.
If the Use Legacy LookML Runtime legacy feature is disabled, projects on the instance will use the new LookML runtime by default. LookML developers can add new_lookml_runtime: no to a project to override the instance default and use the legacy LookML runtime.
For example, if the Use Legacy LookML Runtime legacy feature is disabled for your instance, you can add the new_lookml_runtime: no statement to the project's manifest file to use the legacy LookML runtime for the project:
new_lookml_runtime: no
If your project does not have a manifest file, you can create one using the Looker IDE.
Considerations
When the new LookML runtime is enabled for a project, the LookML validator may catch previously overlooked errors. See the Error: Unknown or Inaccessible Field Best Practices page for more information on how to resolve these errors.
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Hard to understand","hardToUnderstand","thumb-down"],["Incorrect information or sample code","incorrectInformationOrSampleCode","thumb-down"],["Missing the information/samples I need","missingTheInformationSamplesINeed","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-25 UTC."],[],[],null,["# new_lookml_runtime\n\n\u003cbr /\u003e\n\nUsage\n-----\n\n```\nnew_lookml_runtime: yes\n```\n\nDefinition\n----------\n\n| **Caution:** Using the legacy LookML runtime is highly discouraged, especially for [Looker (Google Cloud core)](/looker/docs/looker-core-overview) instances.\n\nThe new LookML runtime provides faster [LookML validation](/looker/docs/2512/lookml-validation#validating_your_lookml) and [content validation](/looker/docs/2512/content-validation), more performant loading of [Explores](/looker/docs/2512/creating-and-editing-explores) and [dashboards](/looker/docs/2512/viewing-dashboards), and faster SQL query writing, among other performance improvements.\n\nYou can use the `new_lookml_runtime` parameter to override your Looker instance's default LookML runtime. The default runtime for projects on your instance is configured with the [**Use Legacy LookML Runtime**](/looker/docs/2512/legacy-feature-schedule#new_lookml_runtime) legacy toggle:\n\n- If the **Use Legacy LookML Runtime** legacy feature is enabled, projects on the instance will use the legacy LookML runtime by default. LookML developers can add `new_lookml_runtime: yes` to a project to override the instance default and enable the new LookML runtime for the project.\n- If the **Use Legacy LookML Runtime** legacy feature is disabled, projects on the instance will use the new LookML runtime by default. LookML developers can add `new_lookml_runtime: no` to a project to override the instance default and use the legacy LookML runtime.\n\nFor example, if the **Use Legacy LookML Runtime** legacy feature is disabled for your instance, you can add the `new_lookml_runtime: no` statement to the project's [manifest file](/looker/docs/2512/reference/param-project-manifest) to use the legacy LookML runtime for the project: \n\n new_lookml_runtime: no\n\nIf your project does not have a manifest file, you can [create one](/looker/docs/2512/other-project-files#creating_a_manifest_file) using the Looker IDE.\n\nConsiderations\n--------------\n\nWhen the new LookML runtime is enabled for a project, the LookML validator may catch previously overlooked errors. See the [Error: Unknown or Inaccessible Field](/looker/docs/2512/best-practices/error-unknown-or-inaccessible-field) Best Practices page for more information on how to resolve these errors."]]
