ALTSTATE File

What are ALTSTATE files and how to open them

Are you having problems opening an ALTSTATE 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 ALTSTATE files.

What is an ALTSTATE file?

An .ALTSTATE file is an Altirra Save State file.

Altirra Save State is a snapshot file created by the Altirra Atari 8-bit computer emulator. It freezes the entire emulated hardware state - including CPU registers, memory contents, peripheral settings, display logic, disk and tape activity - so you can later restore the emulator to exactly that moment. This lets you pause a game or program and return to that exact point later.

This format was used in earlier versions of Altirra (prior to version 3.90) as the v1 save-state format. Newer versions use a different format called v2 and files with the extension .atstate2, which are based on JSON inside a zip file. The old Altirra Save State format is now only loadable by the emulator but not writable in current versions.

Files written in this format begin with the ASCII header AltSave followed by control-characters (hexadecimal sequence 41 6C 74 53 61 76 65 0D 0A 1A), which identifies the beginning of the file and distinguishes it from the newer version.

How to open ALTSTATE files

Important: Different programs may use files with the ALTSTATE file extension for different purposes, so unless you are sure which format your ALTSTATE 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 17, 2026

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