~I File

What are ~I files and how to open them

Are you having problems opening a ~I 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 ~I files.

What is a ~I file?

A .~I file is an AZZ Cardfile Index file.

AZZ Cardfile Index files (.~i) are part of the internal storage format used by AZZ Cardfile (version 3.x and similar) to manage large card files efficiently. When an AZZ Cardfile data file (.azz) is opened, the software unpacks it (since it's ZIP-based), and splits the contents into two related files: the index file with extension .~i, and the "heap" or card-contents file with extension .~h.

The index file serves as a directory listing of all cards stored in the heap. It contains metadata about each card - such as card title ("TITLE"), creation time ("CREATED"), last-opened time ("LAST OPEN"), unique ID ("UID") and smaller descriptors (e.g. "SIZ", "ADR") - but does not include the full card body. This allows AZZ Cardfile to load the index rapidly without reading large content data, improving responsiveness when opening or listing cards.

Technically the .~i file begins with ASCII text signature ".~AZZ CARDFILE AZZ FILE VERSION~" at offset zero, and includes recognizable internal tags such as "~ULT OPEN~", "~CREATED~", "~TITLE~", "~SIZ~", "~UID~", "~ADR~". This distinguishes it from the heap file, which holds the bulk of card content.

How to open ~I files

Important: Different programs may use files with the ~I file extension for different purposes, so unless you are sure which format your ~I 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 14, 2026

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