AS3PROJ File

What are AS3PROJ files and how to open them

Are you having problems opening an AS3PROJ file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your AS3PROJ files.

What is an AS3PROJ file?

An .AS3PROJ file is a FlashDevelop ActionScript 3 Project file.

FlashDevelop ActionScript 3 Project files hold the definitions and settings for a project built in FlashDevelop, an integrated development environment tailored to ActionScript 3 and related Flash/Web technologies. They record where the source files are, how to compile them, what libraries are required, and how to produce the final output (such as a SWF), including compiler options, embed assets, paths, and other build metadata.

These files are created and maintained by FlashDevelop when setting up or saving an AS3 project. The software writes the file in XML form so that all project parameters - source/class paths, compile targets, output file settings, embedded assets, runtime/shared libraries, and build commands - are stored in a structured, editable way. The IDE reads this file on project load to restore the project setup.

Internally this format begins with an XML declaration (encoding UTF-8) and a root element named "project". It contains many keyworded XML nodes and attributes such as INCLUDELIBRARIES, EXTERNALLIBRARYPATHS, OPTION SHOWACTIONSCRIPTWARNINGS, COMPILETARGETS, MOVIE WIDTH/HEIGHT/FPS/BACKGROUND, and sections labeled like "-- CLASS FILES TO COMPILE …", "-- RUNTIME SHARED LIBRARIES …", "-- OUTPUT SWF OPTIONS …", "-- EXECUTED BEFORE BUILD …", among others. These help identify the file reliably.

How to open AS3PROJ files

Important: Different programs may use files with the AS3PROJ file extension for different purposes, so unless you are sure which format your AS3PROJ file is, you may need to try a few different programs.

While we have not verified the apps ourselves yet, our users have suggested seven different AS3PROJ openers which you will find listed below.

Last updated: August 20, 2026

Various apps that use files with this extension

These apps are known to open certain types of AS3PROJ files. Remember, different programs may use AS3PROJ files for different purposes, so you may need to try out a few of them to be able to open your specific file.

Help us help others

File.org helps thousands of users every day, and we would love to hear from you if you have additional information about AS3PROJ file formats, example files, or compatible programs. Please use the links below or email us at submit@file.org to discuss further.