EFU File

What are EFU files and how to open them

Are you having problems opening an EFU 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 EFU files.

What is an EFU file?

EFU files have multiple uses, and Epson Firmware Update Package is one of them. Read more about the other uses further down the page.

Epson Firmware Update Package

We have not yet analyzed in detail what these files contain and what they are used for. We're working on it.

How to open EFU files

Important: Different programs may use files with the EFU file extension for different purposes, so unless you are sure which format your EFU 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 EFU opener which you will find listed below.

Last updated: August 6, 2026

All known file formats using extension .EFU

While Epson Firmware Update Package is a popular type of EFU-file, we know of 2 different uses of the .EFU file extension. Different software may use files with the same extension for different types of data.

Everything File List

Everything File List (.efu) files are snapshots of files and folders exported by the Everything search utility by Voidtools. They are used to capture a fixed listing of files - including their names, sizes, dates, and attributes - for sets of files that do not change often, such as files on a read-only medium or network share. The listing can be loaded into Everything and treated like a live index: you can search, sort and browse through it even when the actual files are offline.

Everything writes .efu files by exporting search results, dragging files into its File List Editor, saving current indices or using command-line tools. When Everything reads an EFU file, it imports the file metadata from the list rather than rescanning disks, letting you work offline or with archived content. EFU files are useful for preserving a snapshot at a point in time, for backup catalogs or when the storage medium is not always available.

Technically, EFU is a plain text file in UTF-8, formatted as a comma-separated values (CSV) document. It begins with a header row that names columns (Filename is required; Size, Date Modified, Date Created, Attributes are optional). Size is stored in bytes; dates are either Windows FILETIME (number of 100-nanosecond intervals since January 1, 1601) or ISO 8601 format. File attributes may use decimal or hexadecimal numeric values. If a field contains commas or double quotes, values are quoted and quotes inside fields are doubled. The file always starts with the ASCII string "Filename,Size,Date…" in its header row.

EFU opener for Windows

We have identified one EFU opener that is compatible with this specific type of EFU file.

Various apps that use files with this extension

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

Help us help others

File.org helps thousands of users every day, and we would love to hear from you if you have additional information about EFU file formats, example files, or compatible programs. Please use the links below or email us at submit@file.org to discuss further.