Article for Website Compass magazine

Big Things In Small Packages
Compressing Large Files to Send on the Internet

If it hasn’t happened yet, it will. Someone sends you an e-mail message with a file attachment so large you can’t open it. Or, perhaps you are the perpetrator. You have sent a byte-heavy attachment that bounces back to your e-mail Inbox with a “message undeliverable” error message.

Most of the time, small image files (such as small JPEG photos) or text-based files (such as Microsoft Word documents) can be sent as e-mail attachments without any problems. But as more people are now sending memory hogs such as large video clips, high-resolution photos, and huge databases, the chances of e-mail rejections due to recipients e-mail memory constraints have greatly increased. The answer lies in compression—sometimes called “zipping” or “stuffing”—your files.

Like its name suggests, compression involves compacting a file into a less-memory intensive version of its original self. Once it’s compressed, it can be more easily sent to the recipient, who then must decompress the file to return it to its original, usable state.

When thinking of file compression, picture a garbage can filled with autumn leaves. The leaves may come up to the top of the can, but if you smash the leaves down, the same number of leaves require far less storage space.

There are no hard-and-fast rules about when you should compress a file before you e-mail it, but a good rule of thumb is to compress files that are larger than half a megabyte (MB) (500 kilobytes [KB]). Most e-mail programs and firewalls can accommodate files smaller than this, although this can vary widely.

Compressing files in the 250- to 500-kilobyte range, however, also can be useful. Files of this size usually can be sent as e-mail attachments with no problems, but without compression they can take too long to open, especially on older, slower computers.

The good news about file compression is that doing it is not difficult. All you need is one of the easy-to-use free or inexpensive utilities on the market that let you compress and decompress files.

The most-common file compression utilities around are PKWARE’s PKZIP, WinZip Computing’s WinZip and Aladdin Systems’ StuffIt. Most compressed files you will come across have been compressed with a version of one of these software utilities.

PKZIP. The folks at PKWARE are the file-compression pioneers who invented the ZIP standard for compressing files back in the ’80s. (Why do you think file compression is often called “zipping” a file?) Files created with a version of PKZIP have a .ZIP file-name extension.

PKZIP’s basic versions, which run on the Windows and UNIX platforms, can be downloaded for free from the PKWARE website ( These versions are great if you just occasionally need to compress or decompress files. For more-frequent users, PKZIP versions with more features and functionality, such as the capability to decompress non-ZIP archived files and create self-extracting archive files, are available from the website’s PKZIP Store.

WinZip. WinZip Computing’s WinZip is the most universal file-compression software around for Windows’ users. In fact, it’s been one of the most popular shareware downloads on the Internet for years.

WinZip Computing lets you download full and beta versions of WinZip for free from its website ( WinZip’s popularity (besides the fact that many copies are freebies) comes from its ease of use and because newer versions can open most if not all compression formats you will come across as e-mail attachments and on the Internet.

WinZip also comes with WinZip Self-Extractor Personal Edition, which lets you create self-extracting archive files (often with the .SEA file-name extension). A self-extracting file is a compressed .ZIP file that is automatically decompressed by the recipient just by double-clicking its icon.

Single- and multi-user licensed versions also can be bought and downloaded from the site.

StuffIt. Aladdin Systems’ file-compression offering works similar to PKZIP and WinZip, with versions available for Windows, Macintosh and Linux. Compressed files created with StuffIt versions have the .SIT file-name extension.

StuffIt Expander is the free version of the software for Windows and Macintosh users that’s available to be downloaded at StuffIt Expander enables users to open most compression files on the Internet. Enhanced features, such as the ability to create self-extracting archive files, are available on StuffIt versions that can be bought at the website’s online store.

Installing and using a file-compression utility provides the easiest way to share large files through e-mail or over the Internet without causing technical problems for yourself and your online friends.


Extend Your File-Compression Knowledge
The most common file-compression types are created by the various versions of PKZIP, WinZip and StuffIt. The file-name extensions are .ZIP for PKZIP and WinZip and .SIT for StuffIt.

However, you might occasionally come across compressed files that do not end in .ZIP or .SIT. Here’s a partial list to guide you through the file-compression alphabet soup.

  • .ARJ—Archive Robert Jung. An archiving program for Windows, MS-DOS, and other PC operating systems.
  • .HQX—BinHex. The BinHex utility creates compressed files in Macintosh operating systems.
  • .RAR—RSS archive retrieval. A compression format often used in newsgroups to compress large files such as movies and other video files.
  • .SEA—self-extracting archive. A file-compression type that allows the recipient of a compressed file to double-click its icon to decompress it.
  • .TAR—tape archive. Files compressed in the UNIX operating system will have the .TAR file-name extension. .TAR files are not actually compressed, but are instead a collection of files that can be extracted from one larger file.
  • .Z or .GZ—GZip. GZip (or gnu zip) is a UNIX file-compression utility that also can be used in MS-DOS.