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A78 file: what it is and how to open it

Atari 7800 ROM. Here is what a .a78 file contains, how to open one on any device, and a viewer that opens it right in your browser.

Open a .a78 file hereChoose fileRead in your browser. Nothing is uploaded.

What the viewer shows

  • Whether the file matches the .a78 signature
  • The first bytes as hex
  • A preview when your browser can display it

What is a .a78 file?

A .a78 file is an atari 7800 ROM. Its registered MIME type is application/x-atari-7800-rom, which places it in the application or document family of formats.

A78 is a binary format: the contents are not readable text, so opening it in a text editor shows scrambled characters.

A78 file format details

Extension.a78
FormatAtari 7800 ROM
MIME typeapplication/x-atari-7800-rom
CategoryApplication or document
Text or binaryBinary
File signatureNone fixed
Registered with IANANo
Other extensionsNone

How to open A78 files

WindowsA78 files (Atari 7800 ROM) are made by specific software. The reliable way to open one is with the program that created it; a generic viewer will only show raw data.
MacThe same applies on a Mac: look for a Mac version of the program that makes A78 files.
iPhone and iPadPhones rarely open this type of file directly. The viewer above can show what is inside it without installing anything.
AndroidThe same applies on Android. The viewer above shows the first bytes of the file so you can confirm what it is.

Can you convert a .a78 file?

TapToConvert does not convert A78 files. The usual route is to open the file in the program that made it and use its Export or Save as option.

A78 file FAQ

What is a .a78 file?

A .a78 file is an atari 7800 ROM, with the MIME type application/x-atari-7800-rom.

How do I open a .a78 file?

With the program that created it. The viewer on this page shows what is inside without installing anything.

Is a .a78 file safe to open?

A78 files hold data rather than programs, but any file from an unknown source can be crafted to exploit the software that opens it. Keep that software up to date. The viewer on this page only reads the bytes and never runs anything.

What is the MIME type of .a78?

application/x-atari-7800-rom. Web servers send this type so browsers know how to handle the file.

Is A78 a text or binary format?

Binary. Its contents are not readable as text.

File type facts come from the IANA media type registry, the mime-db project and the freedesktop.org shared MIME database.

Similar file types

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