File compression basics

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Overview

Almost all the files on the Nexus sites are compressed in to what are known as "archives". The file formats for these archives will usually be either .zip, .rar or .7z.

Benefits and reasons for file compression and archiving

Archives are beneficial for two reasons.

One file

File compression software packages multiple files in to one simple to use file. Instead of you having to download many different files you will only have to download a single file that contains all the other files within it. If the file author has packaged the archive correctly, then all the files and folders will be in the proper structure and directories, saving you a heck of a lot of time.

Reduced file size through compression

During the packaging phase the total file size of the archive should be reduced; sometimes by just a little and sometimes significantly depending on what type of files are being archived. It's not unheard of for file archives to be anywhere from 10% - 50% smaller in size than the sum total of all the files in the archive uncompressed. Archive compression is lossless, meaning no data is lost, even though the files use up less space.

Compression software and preferences

When it's all said and done, I prefer 7-Zip over everything else. It has the best compression, it's free, the source code is freely available and you can decompress all common archive formats and create .7z or .zip archives.

  • If you want the best compression to save space, download and upload time, use the .7z format.
  • If you want the best speed during compression and best portability, use the .zip format (even older and non-Windows operating systems can open them natively).
  • The .rar format is a middle-of-the-road proprietary file format.

Also recommended is the freeware program IZArc (www.izarc.org) for Windows Vista/7/8/10, as it is capable of packing and unpacking all common archive and CD-image formats.

Most common archive formats (2016)

  • Filetype extension: .7z*
  • Commonly referred to as: 7-Zip (or SevenZip)
  • Website: 7-Zip, more info here: Installation of 7-Zip
  • Cost: FREE
  • License: Open Source, GNU LGPL
  • Compression: Best
  • Portability: To extract files in this format, each user must have 7-Zip or the latest version of WinRAR installed
  • Native support in Windows and OS X?: No


  • File extension: .rar
  • Commonly referred to as: RAR
  • Website: RARLAB
  • Cost: $30
  • License: Trialware
  • Compression: Better than OK
  • Portability: To extract files in this format, each user must have WinRAR, 7-Zip, or similar compatible program.
  • Native support in Windows and OS X?: No


  • Filetype extension: .zip
  • Commonly referred to as: Zip
  • Website: WinZip
  • Cost: $35
  • License: Trialware
  • Compression: OK
  • Portability: This format has been around so long that just about every program that deals with compression can handle it.
  • Native support in Windows and OS X?: Yes

Compression size comparison

NOTE: These comparisons are outdated and use old versions of the software.

  • Oblivion mod to compress: Apophis: Armory of the Silver Dragon 0.9.3
  • Oblivion mod uncompressed size: 151 MB


  • Archive Program: 7-Zip v4.65
  • Compression Setting: Maximum
  • Time to Compress: 0 minute, 33 seconds
  • Time to Decompress: 0 minute, 5 seconds
  • Final compressed size: 55.5 MB


  • Archive Program: WinZip v14.5
  • Compression Setting: Best Compression (non-compatible)
  • Time to Compress: 0 minute, 59 seconds
  • Time to Decompress: 0 minute, 7 seconds
  • Final compressed size: 63.2 MB


  • Archive Program: WinRAR v3.93
  • Compression Setting: Best
  • Time to Compress: 0 minute, 13 seconds
  • Time to Decompress: 0 minute, 3 seconds
  • Final compressed size: 74.5 MB


  • Archive Program: WinZip v14.5
  • Compression Setting: Legacy (Zip 2.0 compatible)
  • Time to Compress: 0 minute, 40 seconds
  • Time to Decompress: 0 minute, 4 seconds
  • Final compressed size: 75.5 MB


NOTE: The above results were from using the 32-bit versions of the programs on a Windows 7, 64-bit operating system.

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