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For a tutorial on how to develop scripts for CLEO, see CLEO/Tutorial.
CLEO 4 logo
Current version:San Andreas 4.3.22
Vice City
Developed by:User.pngSeemann, Alien, User.pngDeji,
User.pngDK22Pac, User.pngThirteenAG
Supported games:GTA 3, GTA VC, GTA SA
Type:mission scripting

CLEO Library or shortly CLEO is a tool that extends coding possibilities in GTA 3 series games by adding a lot of new opcodes and allowing to run the scripts without modifying the main.scm. CLEO was created and originally developed by Seemann. CLEO 4 was initially developed by Alien, now it's continued by Deji.


Extra opcodes

CLEO adds a lot of useful opcodes making possible file management, game memory handling, calling exe functions, playing audio files and much more. New opcodes were added in the fourth version to work with audio streams, to format strings, to display custom texts on screen without using external text files (.fxt, .gxt).


This section is incomplete. You can help by fixing and expanding it.

Custom scripts

The main feature of CLEO is that it allows running custom scripts (commonly a single file with the extension .cs) without starting a new game. All you need is to get a script, place it in the CLEO folder and run the game (new or saved). This feature is recognized as one of the most important achievements in GTA SA modding.

Known issues

  • CLEO cannot work with SA v2.00 and higher. One should use a downgrade patch.
  • Using mp3 related opcodes in CLEO 3 could cause occasional crashes of the game. CLEO 4 is more stable on this matter
  • Some CLEO features don't work in multiplayer mods such as SA:MP due to their anti-cheating measures
  • Complex scripts developed for CLEO 3 (most notably those ones made by Japanese modder Ryosuke) may not work with CLEO 4. A special compatibility mode was introduced in CLEO 4.3 to solve this problem

Major projects using CLEO

CLEO for GTA III and Vice City

Initially, CLEO was designed and made for San Andreas. The huge success of it and popularity of previous games inspired Alien to port the library for GTA 3 and Vice City, without some features, such as custom saves storing CLEO variables and scripts state. After Alien's retirement, the development slowed down until Silent issued a version with some fixes. Soon after that DK22Pac announced the next version of CLEO for GTA III and Vice City, written from scratch. It was never released, but ThirteenAG helped to finish his work and the second version is now available for download.

CLEO Android

CLEO Android is an official fork of the CLEO Library made by Alexander Blade for the Android platform.

This section is incomplete. You can help by fixing and expanding it.

External links