Compression Files Used for Sending Out Data



To inform you of the use of the 7-Zip file archiver program – providing need and explanation.  This is not an endorsement – only an informative discussion.


In responding to data requests for Idaho’s Special Conservation Status Species, IFWIS staff compile selections of shapefiles, PDFs, and supporting documents.  These requests often result in a large collection of files and subsequently large file sizes for emailing the results to partners and customers.  The easiest and most traditional method to aide in sending large files has been to ZIP the folders/files.  However, sometimes this still does not result in a small enough file size for emailing or receipt.  Other compression types have also been used, such as BZIP, GZIP and TAR, among others.  Recently, when ZIP is not enough, I have been using a newer file compression format called 7‑Zip (7z) that has significantly outperformed all previous freeware compression types.  For example, a recent collection of uncompressed files totaling 168MB resulted in compressed file sizes of 95MB ZIP and 6MB 7z.  The 7‑Zip software for Windows is available in both 32 and 64‑bit installs at  Note that this is an .org web site and that each downloadable installer is 1MB for the current 9.20 version.  Caution – I have had two customers who have encountered issues while installing.  When I send customers 7z files, I also provide instructions to download and install the free 7‑Zip open source software.  One customer responded that they ended up with WinZip while the other downloaded MegaZipper.  In the multiple times that I have visited this site, I have never encountered these links – not to say that they’re not there, so please be aware.

If you have better information or another useful tool, please add a new comment to improve this Blog.

Example E-Mail Message

“Attached you will find your requested data.  Please note that the attached data file has a '7z' extension.  This is a 7-Zip compressed file.  7-Zip is freely available, open source software for file compression ( and currently seems to be the best compression software, significantly outperforming win-zip.  The attached compressed files are 6 MB, while these same files were 95 MB in .zip format (168 MB uncompressed).  If you have a problem or concern with downloading or using this software, please let me know.  I’ll be happy to provide the data differently.”

7-Zip Description

7-Zip is open source software and is a file archiver with a high compression ratio. The program supports:

  • Packing / unpacking: 7z, XZ, BZIP2, GZIP, TAR, ZIP and WIM
  • Unpacking only: ARJ, CAB, CHM, CPIO, CramFS, DEB, DMG, FAT, HFS, ISO, LZH, LZMA, MBR, MSI, NSIS, NTFS, RAR, RPM, SquashFS, UDF, VHD, WIM, XAR and Z.