What is the AU3 file format?
An .au3 file is a plain-text script written in the AutoIt v3 scripting language, designed for automating the Windows GUI and general Windows scripting tasks. AutoIt was created by Jonathan Bennett and is maintained by the AutoIt Team; v3, released in 2004, introduced the .au3 extension as the standard source file name.
AutoIt v3 uses a BASIC-like syntax with built-in functions for simulating mouse clicks, keyboard input, window manipulation, and file system operations. Scripts can automate virtually any Windows application without requiring an exposed COM or API interface.
.au3 scripts are executed directly by the AutoIt3.exe interpreter or compiled into a self-contained .exe using the bundled Aut2Exe tool. Because malware authors frequently abuse AutoIt to wrap malicious payloads, many antivirus engines flag compiled AutoIt executables as suspicious regardless of actual content.
The bundled SciTE4AutoIt3 editor provides syntax highlighting, a debugger, and one-key compilation (F7). Visual Studio Code supports .au3 via community extensions.
Key language features include:
#includefor code reuse and library imports#RequireAdmindirective to request UAC elevationFunc/EndFuncfunction definitionsDllCall()for native Windows API accessObjCreate()for COM object automation
The compiled intermediate format .a3x is a tokenised bytecode variant used for faster loading without full native compilation. Unlike .au3, .a3x files are not human-readable.
Security & safety
RISK: HIGHAutoIt is heavily abused by malware authors as a RAT/dropper layer. Compiled AutoIt .exe files trigger high false-positive rates in AV products. When receiving an .au3 file or compiled AutoIt .exe from an untrusted source, inspect the source carefully before running. AutoIt scripts have full access to the Windows API, filesystem, registry, and network. Security researchers commonly decompile suspicious .exe files with myAut2Exe or similar tools to recover the .au3 source.
Format details
in a nutshell- Sun/Oracle AU audio file (legacy) - AU audio format used by Sun Microsystems/NeXT; unrelated, uses numeric header, rarely seen with .au3 extension but possible confusion.
Programs that open AU3 files
Windows4 apps
NotePad++ text editor
Open-source Open the .au3 file directly; install the AutoIt UDFs plugin for syntax highlighting. 
AutoIt3 (runtime + SciTE4AutoIt3 editor)
Free Install AutoIt3 - right-click .au3 → Run Script to execute; Edit Script to open in SciTE4AutoIt3 editor. Press F7 in SciTE to compile to .exe. 
Visual Studio Code
Open-source Install the 'AutoIt' extension (Damien122) for syntax highlighting and IntelliSense, then open the .au3 file. 
macOS1 app
Linux1 app
gedit
Open-source Open as plain text to read; AutoIt does not run natively on Linux (Wine may run compiled .exe). Technical details
deep spec| Language version | AutoIt v3 syntax (not compatible with AutoIt v2 scripts) |
| Encoding | ANSI by default; UTF-8 with BOM required for Unicode string literals |
| Execution | Interpreted by AutoIt3.exe or compiled to .exe via the bundled Aut2Exe tool |
| Compiled intermediate | .a3x - tokenised/compressed bytecode; .exe wraps an AU3! signature payload |
| Platform | Windows only (Windows 95 through Windows 11 supported) |
| IDE / editor | SciTE4AutoIt3 (bundled - syntax highlighting, debugger, compiler); VS Code via extension |
| Compile shortcut | F7 in SciTE4AutoIt3 triggers Aut2Exe compilation |
| AV detection risk | Compiled .exe frequently flagged by heuristic AV engines due to widespread malware abuse of AutoIt |
| Key directives | #include, #RequireAdmin, #NoTrayIcon, #OnAutoItStartRegister |
| Windows API access | DllCall() for native API calls; ObjCreate() for COM object automation |
| Typical size | 1 KB - 500 KB (source); multi-MB when compiled with bundled resources |
| Container | Plain text (source file); binary PE executable (compiled output) |
| Released | 2004 (AutoIt v3.0) |
| Latest version | AutoIt 3.3.16.1 (2022) |
| Specification | www.autoitscript.com |
AU3 conversions
Community Q&A
asked by usersNo questions yet - be the first to ask about AU3 files.
