# Configuring preloaded execution

> Environment variables for controlling preloaded executor behavior in UiPath Robot.

You can manage the behavior of preloaded executors by setting specific environment variables on the robot machine. Preloaded executors exist only in User Mode, so the variables in this table have no effect in Service Mode:

| Environment variable | Value | Description |
| --- | --- | --- |
| `UIPATH_PRE_LOADED_EXECUTOR` | `Legacy`, `Windows`, `Portable`, or `None` | Sets which executors the Robot preloads: `Legacy` for Windows - Legacy projects, `Windows` for Windows projects, and `Portable` for cross-platform projects. To preload several, separate the values with commas, for example `Windows, Legacy`. The values aren't case-sensitive. `None` overwrites the default behavior and starts the preloaded executor only when the first job starts. If the variable isn't set, the Robot preloads `Windows` and `Legacy` on Windows, and `Portable` on other operating systems. |
| `UIPATH_DISABLE_PRE_LOADED_EXECUTOR` | `True` | Disables the preloaded executor. |

Preloaded executors apply to RPA processes and test cases, which run in the Robot Executor. Agents, functions, and API workflows run in executor packages, which the variables above don't affect. The executor packages run in a separate host process, which you can preload with the following variables:

| Environment variable | Value | Description |
| --- | --- | --- |
| `UIPATH_EXECUTORS_HOST_PRELOAD` | `Off` (default) or `On` | `On` starts the executor hosts when the Robot connects to Orchestrator, instead of when the first job starts. In Service Mode, it has no effect when `UIPATH_HEADLESS_WITH_USER` is set. |
| `UIPATH_PRELOADED_RUNTIMES` | Executor package names, separated by `;`, `,`, or `:` | With preloading on, limits it to the named [executor packages](https://docs.uipath.com/robot/standalone/2026.10/admin-guide/executor-packages). If the variable is empty, the Robot preloads every executor package that the Executors feed offers. |