04.04.2020 (Saturday)

FUPX - Quick Start

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Last modified: 17.09.2018




FUPX is a graphical interface for the UPX. It offers easy access to all documented and undocumented UPX parameters without the need for command line usage. The program works with the last four versions of the UPX: 3.91, 3.92, 3.93, 3.94, 3.95 (32 and 64-bit). The active UPX version can be set in the program options.

FUPX is a free software, and can be used both for personal and commercial use.
The author of the program FUPX is Jacek Pazera.
Program home page:

UPX (Ultimate Packer for eXecutables)

UPX is a free and open source executable packer supporting a number of file formats from different operating systems, including Portable Executable (PE) files (the most of EXE, DLL, OCX, CPL files used on Microsoft Windows systems), ELF executables (used on Unix, Linux, Solaris, FreeBSD and other operating systems), ARM executables and others.

After packing (compressing) executable file by the UPX, the resulting file remains executable and can be used in the same way as the original file. UPX uses a high efficient compression algorithms and achieves very good compression ratio, typically much better than WinZip/zip.

On Windows platform, UPX can pack 32 and 64 bit executable files produced according to Microsoft Portable Executable and COFF Specification (EXE, DLL, OCX, BPL, CPL, AX and other), but support for 64 bit files is currently declared as experimental. .NET executables are not supported.

The authors of the UPX are Markus F.X.J. Oberhumer, László Molnár & John F. Reiser.
UPX home page:

Main window

After starting the program displays the main window:

FUPX main window
FUPX main window

At the top of this window is the main menu, which gives you access to most functions of the application.
Below is a toolbar for easy access to frequently used operations.
In the central part of the window is a file list.
In the lower part there are four expandable panels: Profile, Output file name, UPX settings and Command line.

Compressing (packing) files

To pack executable files, you must first add them to the list. To do this, click the Add files button in the toolbar. Will be displayed a standard dialog box for file selection, in which you have to select one or more executable files, and click Open button. You can also add files to the list using the drag and drop technique. When you do this, the program analyzes the selected/dropped files and each executable file is added to the processing list, not executables (eg. text files without extension) are ignored. If the file is already compressed by UPX, it is marked on the list by green color. To start the compression, on the list must be at least one unpacked file, moreover, it must be checked in the Active column.

When you perform the above steps, click the Compress button. A new window appears, where you can track the compression process.

Decompressing (unpacking) files

First, you need to add to the list some executable files packed with UPX. Also make sure that the files you want to decompress are checked in the Active column. Then click the Decompress button. A new window appears, where you can track the decompression process.

Compression parameters

If you ran the program for the first time and have not changed any compression parameters, will be used default UPX settings. You can change the compression parameters by selecting one of the predefined profiles (on the Profile panel), or by manually setting the desired parameters on the UPX settings panel and the Advanced UPX settings tab.

If you want to reset all UPX settings to default values, select menu UPX -> Default settings.

Managing file list

You can activate/deactivate any files in the list by checking/unchecking desired files in the column Active. Only the checked files will be processed during compression and decompression.

You can filter the files in the list based on multiple criteria. When the filter is enabled, all files excluded by the filter are hidden and will not be processed during compression, decompression and removing.

If you want to remove from the list some files, check them in the Active column and click Remove button on the toolbar. All checked files will be removed from the list (but not from disk!). If you want to remove from the list all visible (not filtered) files, select menu File list -> Check all files, then click the Remove button.

You can change the location of files in the list using the drag and drop. Similarly, you can move the columns. If you want to show or hide some column, right-click on the file list header, and in the context menu, select or deselect the desired column.
You can sort (ascending or descending) the displayed information by clicking the appropriate column header.

Main menu & toolbar

Loading & saving settings

When you close the program, all compression settings are saved to the file __Last.ini in the profiles directory. The next time you run application, compression settings are loaded from this file.

The rest of the application settings (main window size and location, columns order and visibility, current color scheme and many others) are stored in the file fupx.ini in the program main directory. Of course, these settings are also loaded at the next startup.


The program does not use system registry and all settings are stored in the above-mentioned files. If you want, you can copy all files (including whole directory structure) to the USB drive, and run the program from that drive on other computers.
You can also download the program in the form of a 7-Zip archive and extract it to an external drive.