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Scripting & Security

The ability to include Python scripts within blend files is valuable for advanced tasks such as rigging, automation and using the game-engine, however it poses a security risk since Python doesn't restrict what a script can do.

Therefore, you should only run scripts from sources you know and trust.

Automatic execution is disabled by default, however some blend files need this to function properly.

When a blend file tries to execute a script and is not allowed, a message will appear in the header with the option to Reload Trusted or Ignore the message.

Python Script AutoExec Header.png

Scripts in Blend Files

Auto Execution

Here are the different ways blend files may automatically run scripts.

  • Registered Text-Blocks
    A text block can have its Register option enabled which means it will load on start.
  • Animation Drivers
    Python expressions can be used to drive values and are often used in more advanced rigs and animations.
  • Game Engine Auto-Start
    scripts are often used for game logic, blend files can have auto-start enabled with runs the game on load.

Manual Execution

There are other ways scripts in a blend file may execute that require user interaction (therefor will run even when auto-execution is off),
but you should be aware that this is the case since it's not necessarily obvious.

  • Running a script in the text editor (ok, this is obvious!).
  • Rendering with FreeStyle - FreeStyle uses scripts to control line styles
  • Running the Game-Engine.

Controlling Script Execution

Blender provides a number of ways to control whether scripts from a blend file are allowed to automatically execute.

First of all, the file-selector has the option Trusted Source which you can use on a case-by-case basis to control auto-execution.

However you may forget to set this, or open a file without going through the file selector - so you can change the default (described next).

Setting Defaults

In the File section of the user-preferences there is the toggle Auto-Run Python Scripts.

This means the Trusted Source option in the file-selector will be enabled by default, and scripts can run when blend files are loaded without using the file selector.

Once enabled you have the option to exclude certain directories, a typical configuration would be to trust all paths except for the download directory.

Python Script AutoExec Configure.png

Command Line

You may want to perform batch rendering or some other task from the command line - running Blender without an interface.

In this case the user-preferences are still used but you may want to override them.

  • Enable with -y or --enable-autoexec
  • Disable with -Y or --disable-autoexec

Example - rendering an animation in background mode, allowing drivers and other scripts to run:

blender --background --enable-autoexec my_movie.blend --render-anim

Note: these command line arguments can be used to start a regular blender instance and will still override the user-preferences.

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This is the old manual!
For the current 2.7x manual see

User Manual

World and Ambient Effects


World Background

Ambient Effects

Stars (2.69)

Game Engine


Introduction to the Game Engine
Game Logic Screen Layout


Logic Properties and States
The Logic Editor


Introduction to Sensors
Sensor Editing
Common Options
-Actuator Sensor
-Always Sensor
-Collision Sensor
-Delay Sensor
-Joystick Sensor
-Keyboard Sensor
-Message Sensor
-Mouse Sensor
-Near Sensor
-Property Sensor
-Radar Sensor
-Random Sensor
-Ray Sensor
-Touch Sensor


Controller Editing
-AND Controller
-OR Controller
-NAND Controller
-NOR Controller
-XOR Controller
-XNOR Controller
-Expression Controller
-Python Controller


Actuator Editing
Common Options
-2D Filters Actuator
-Action Actuator
-Camera Actuator
-Constraint Actuator
-Edit Object Actuator
-Game Actuator
-Message Actuator
-Motion Actuator
-Parent Actuator
-Property Actuator
-Random Actuator
-Scene Actuator
-Sound Actuator
-State Actuator
-Steering Actuator
-Visibility Actuator

Game Properties

Property Editing

Game States



Camera Editing
Stereo Camera
Dome Camera




Material Physics
No Collision Object
Static Object
Dynamic Object
Rigid Body Object
Soft Body Object
Vehicle Controller
Sensor Object
Occluder Object

Path Finding

Navigation Mesh Modifier

Game Performance

Framerate and Profile
Level of Detail

Python API

Bullet physics


Standalone Player
Licensing of Blender Game

Android Support

Android Game development