A4W File

What are A4W files and how to open them

Are you having problems opening an A4W 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 A4W files.

What is an A4W file?

An .A4W file is an Apple II Oasis For Windows Savestate file.

The Apple II Oasis For Windows Savestate format is a file type used by the Apple II Oasis emulator for Windows to capture a complete snapshot ("save state") of the emulated Apple II machine at a single moment. This includes the CPU registers, memory (RAM), attached disks, and most other hardware state so that emulation can be paused and resumed exactly where it left off. These files let users save their progress without using the emulator's in-emulated save routines (if any).

A .A4W file is written exclusively by Apple II Oasis for Windows; only that emulator creates these savestate files. When running the emulator, invoking the save state feature causes all current state data to be serialized into a .A4W file. Later, loading that same file restores the exact machine state so programs, games or whatever was running continue as if uninterrupted.

Inside a .A4W file there is a text header followed by binary state data. It begins with "[AppleII]" then a line "Type=SaveState", followed by ASCII-end-of-line and then two 1A bytes (hex 0x1A), which separate the header from the rest of the binary portion. The initial bytes of the file are: 5B4170706C652049495D0D0A547970653D5361766553746174650D0A1A1A at offset 0.

How to open A4W files

Important: Different programs may use files with the A4W file extension for different purposes, so unless you are sure which format your A4W file is, you may need to try a few different programs.

We have not yet verified any programs for Windows that work with this specific file format. If you know one, please use the 'Suggest a program' link below. Thanks!

Last updated: August 16, 2026

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