A78 File

What are A78 files and how to open them

Are you having problems opening an A78 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 A78 files.

What is an A78 file?

An .A78 file is an Atari 7800 ROM file.

Atari 7800 ROM files with the extension .a78 are digital images of game cartridges made for the Atari 7800 video game console. They contain an exact copy of the cartridge's read-only memory so that emulators or flash cartridges can run the same game data that would be stored on a physical cart.

These ROMs are produced by dumping the data off a cartridge using specialized hardware, often by hobbyists or preservationists. The resulting file can then be used by Atari 7800 emulator software or loaded onto certain flash cartridges to play on real hardware. Many ROM collections use .a78 in place of raw binary dumps (.bin) because .a78 can include extra metadata that helps programs interpret hardware requirements correctly.

The .a78 format may begin with a header that provides information like game title, ROM size, hardware mapper type, controller requirements, television format (NTSC or PAL), save-device support, and other cart features. The header starts with a magic ASCII signature "ATARI7800" at byte offset 0, followed later by the text "ACTUAL CART DATA STARTS HERE."

How to open A78 files

Important: Different programs may use files with the A78 file extension for different purposes, so unless you are sure which format your A78 file is, you may need to try a few different programs.

While we have not verified the app ourselves yet, our users have suggested a single A78 opener which you will find listed below.

Last updated: August 16, 2026

Various apps that use files with this extension

These apps are known to open certain types of A78 files. Remember, different programs may use A78 files for different purposes, so you may need to try out a few of them to be able to open your specific file.

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