CLEO

CLEO is an open-source scripting library for running custom scripts in supported GTA games without changing the original game files. Scripts can add game features, missions, engine enhancements, and in-game applications, and can be added or removed while a game is running without starting a new game. Listed games include GTA III, Vice City, San Andreas, GTA IV, Bully, The Trilogy Definitive Edition, re3, reVC, Liberty City Stories, and Vice City Stories. Plugins can extend the scripting runtime, often by adding opcodes for uses such as memory management, text utilities, and audio processing. CLEO Redux supports JavaScript and TypeScript and can run alongside CLEO 5 for supported games. The project provides a CLEO SDK for plugin creators and points script authors to Sanny Builder resources. For general PC installation, the documentation specifies GTA San Andreas PC version 1.0 US and an ASI Loader or equivalent. The download center also lists CLEO iOS as a modloader for GTA: San Andreas. The site directs users to Discord for help and notes that the developers are not affiliated with Take 2 Interactive or Rockstar Games.

CLEO offers script-based modding for a range of listed games, with plugins and developer resources. Check the specific game and platform requirements before installing.

CLEO suits players and modders working with its listed GTA games or Bully on supported platforms. It may also interest script authors who want plugin tools or JavaScript and TypeScript options through CLEO Redux.

Overview

CLEO is an open-source scripting library for adding custom scripts to supported Grand Theft Auto games without changing the original game files. It suits players who want to add missions, features or in-game tools, and modders building scripts or plugins. Its live script management and developer tooling are useful strengths, but compatibility is tied to specific games and builds.

Key features

Scripts can be added or removed while a game is running, without beginning a new save. That makes it practical to iterate on a mod or switch scripts without restarting a playthrough. Scripts can add game features, missions, engine enhancements and in-game applications.

Plugins extend CLEO’s scripting runtime, commonly by adding opcodes; examples include memory management, text utilities and audio processing. CLEO 5 adds modular code with import and export support, runtime checks, debugging utilities, and improvements to audio and plugins. These tools make CLEO more than a player-facing loader: it also supports developers building and maintaining mods.

CLEO Redux adds JavaScript and TypeScript scripting and can run alongside CLEO 5 for supported games. Its permission levels govern potentially unsafe operations such as process-memory access, loading external libraries and network requests. That is a useful control for authors and users, though Redux support for The Trilogy Definitive Edition has limitations.

The CLEO SDK supports plugin creation, while script authors are directed to Sanny Builder resources. For documented PC installation, users extract the release into the game directory; removal means deleting CLEO.asi and, optionally, the CLEO folder. CLEO 5.4 also hardens path validation to block access beyond the game root and settings directories.

Pricing

CLEO is free and open source, with no paid plan described. That makes it accessible to both players and mod authors, but the free price does not remove the need to check that a particular release, game build and platform match.

Platforms

CLEO covers Windows PC and iOS, with supported games also spanning PSP and PS2. The download center describes CLEO iOS as an all-in-one modloader for GTA: San Andreas on iOS, created by squ1dd13. The general PC documentation has a narrower requirement: GTA San Andreas PC version 1.0 US and an ASI Loader or equivalent. Treat platform and game support as release-specific rather than assuming one installation covers every listed title.

Supported games include GTA III, Vice City, San Andreas, GTA IV, Bully, The Trilogy - The Definitive Edition, re3, reVC, Liberty City Stories and Vice City Stories. CLEO’s broad catalog is appealing to players with older or varied GTA installs, but its documented San Andreas PC requirement shows why checking the exact build matters.

Who it's for

CLEO is a strong fit for GTA players who want script-based changes without altering original game files, especially those who value changing scripts mid-session. It also suits developers who need plugin support, debugging utilities or a route into JavaScript and TypeScript scripting through Redux. It is a poor fit for someone seeking a universal mod loader or a straightforward option for an unsupported game build.

Pros and cons

• Pros: Live script additions and removals let players adjust mods without restarting a game or starting a new one.
• Pros: Open-source releases, plugin support, the CLEO SDK and author resources serve both users and mod developers.
• Pros: CLEO Redux permission levels and CLEO 5.4 path validation address sensitive operations and access outside game directories.
• Cons: The general PC installation requirement of San Andreas version 1.0 US plus an ASI Loader or equivalent can rule out other builds.
• Cons: Redux support for The Trilogy Definitive Edition comes with limitations, so players should not assume full compatibility.
• Cons: Help for issues beyond the troubleshooting guide depends on GitHub tickets or Discord rather than a single in-app support path.

Alternatives

Choose MelonLoader if you need a free mod loader spanning Android, Linux, macOS and Windows rather than CLEO’s GTA-focused set of games. SMAPI is the better fit for Stardew Valley players whose game meets its stated version requirement: 1.6.14 or later on Linux, macOS, Windows or Steam Deck.

For Cyberpunk 2077, RED4ext is a free Windows script extender and plugin manager. Satisfactory Mod Loader is aimed at Satisfactory, with Linux server and Windows client and server support and no required dependencies. ScriptHookVDotNet is the relevant choice for PC modding that requires Script Hook V, .NET Framework 4.8 or later, and Microsoft Visual C++ Redistributable.

Baldur's Gate 3 Script Extender is an alternative for Baldur’s Gate 3 on Linux or Windows; its Commons Clause restricts selling software whose value substantially derives from it. BepInEx is a free, open-source option with manual installation and stable and bleeding-edge builds across Linux, macOS and Windows. Cyber Engine Tweaks is another free, MIT-licensed framework for Linux and Windows. Browse Game Mod Loaders for more options.

Verdict

Choose CLEO if you want script-based mods for a supported GTA game and value live script changes, plugin extensibility or developer tools. Its open-source model and breadth of supported games are compelling, but the exact game build and platform determine whether it will work. If your setup falls outside those requirements—or you need a loader for a different game—look elsewhere.