ADN File

What are ADN files and how to open them

Are you having problems opening an ADN 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 ADN files.

What is an ADN file?

An .ADN file is a Lotus 1-2-3 Add-In Application file.

The Lotus 1-2-3 Add-In Application format is a plugin file used by Lotus 1-2-3 spreadsheet software. These files let external routines - called add-in applications or add-in @functions - extend Lotus 1-2-3 beyond its built-in features by offering new menu commands, custom dialog routines, or spreadsheet formula functions. For example, the Macro Library Manager is one such add-in, shipped as MACROMGR.ADN.

Lotus 1-2-3 produces .ADN files and also loads them at runtime: users choose File → Add-In Attach to register and load an .ADN file into memory. Once attached, the add-in can be assigned to invoke via function keys (e.g. ALT-F7) or via custom menu entries. Add-in @functions behave like built-in spreadsheet functions, while add-in applications deliver tasks invoked through menu or key. Lotus adds support for .ADN beginning in Release 2.0.

The format is identified by internal markers: it contains the ASCII strings "1-2-3 ADD-IN", "VERS", "HELP", "MENU", "COPYRIGHT", "CELL", "CALC", "READ", among others, and has a signature of bytes "0x11000200" at offset 2. These markers help Lotus recognize a file as an add-in module.

How to open ADN files

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

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

Last updated: August 17, 2026

Various apps that use files with this extension

These apps are known to open certain types of ADN files. Remember, different programs may use ADN 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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