3X5 File

What are 3X5 files and how to open them

Are you having problems opening a 3X5 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 3X5 files.

What is a 3X5 file?

A .3X5 file is a 3by5 Source file.

3by5 Source (.3X5) is a database/file-management format created by Softshell Corporation for DOS. It is used to store collections of textual "cards" or records - each up to 4800 characters - organized so that users may enter, search, retrieve, edit, and output information in a flexible, menu-driven environment. Users often use it to keep notes, form letters, bibliographic entries, or any data that can be treated as discrete records keyed for search.

The software that creates and uses these files is the 3BY5 program. It writes .3X5 files when you save your collection of cards (records) in 3BY5. Files are retrieved and manipulated by 3BY5 itself; you cannot assume they will work in other programs unless they explicitly support the 3BY5 format.

Files begin with a signature identifying them as 3by5 Source format: the first bytes are the ASCII string "3by5SourceV" (hex 33 62 79 35 53 6F 75 72 63 65 20 56) at offset zero.

How to open 3X5 files

Important: Different programs may use files with the 3X5 file extension for different purposes, so unless you are sure which format your 3X5 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 16, 2026

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