Expression engine

File-based configuration

You can add _FILE to individual variables to provide their configuration in a separate file. Refer to Keeping sensitive data in separate files for more details.

Expressions are the JavaScript snippets n8n evaluates at runtime to set node parameters dynamically. The expression engine is the component that runs that evaluation. This page lists environment variables for configuring it.

Experimental

The vm engine is experimental. n8n runs the legacy engine by default. The variables below other than N8N_EXPRESSION_ENGINE only take effect when you set N8N_EXPRESSION_ENGINE to vm.

Variable	Type	Default	Description
N8N_EXPRESSION_ENGINE	Enum string: legacy, vm	legacy	Which expression engine to use. legacy runs expressions without isolation. vm runs them in a sandboxed V8 isolate. vm is experimental; legacy remains the default.
N8N_EXPRESSION_ENGINE_POOL_SIZE	Number	1	Number of V8 isolates kept warm in the pool.
N8N_EXPRESSION_ENGINE_MAX_CODE_CACHE_SIZE	Number	1024	Maximum number of compiled expressions to cache.
N8N_EXPRESSION_ENGINE_TIMEOUT	Number	5000	Execution timeout in milliseconds for each expression evaluation.
N8N_EXPRESSION_ENGINE_MEMORY_LIMIT	Number	128	Memory limit in MiB for each V8 isolate.
N8N_EXPRESSION_ENGINE_IDLE_TIMEOUT	Number	-	If set, scales the isolate pool to zero warm isolates after this many seconds with no activity.