Here is a guide to many uses of LZW compression and how to avoid it for those curious, despite the fact that the LZW patent expired in 2003. Converting to non-LZW solutions gives full freedom of choice of software, especially free software which has lacked LZW support to avoid past patent issues and licensing with Unisys. The LZW patent expired around June 20, 2003. Even though the patent is expired, it makes sense to switch your LZW-based formats to non-LZW formats anyways for the simple fact that they are better and in some cases more common and more widely supported by programs on more types of computers, especially free software that lacks LZW support. Also, software and formats that replace LZW are useable even on computers back to at least the early 1990's, if not earlier.
For the typical home user, the conversion would only include converting GIFs to PNGs (similar or smaller file size than GIFs) and LZW-compressed TIFFs to uncompressed TIFFs (larger than TIFF LZW) or PNGs (smaller than TIFF LZW with same quality). The US Department of Defense mandated as shown in a 1999 specifications document that the default graphics format for use is to be PNG for lossless graphics (preserves all original information like GIFs) and JPEG for lossy graphics. Some people may also have some PDFs they have created using older programs using LZW or really old compressed archives made by pre-1993 programs (the original versions of ZIP and StuffIt, among others) or UNIX Compress .Z. Unisys has even been wanting people to license LZW to allow posting of LZW-encoded PDFs on a website.
Make sure your PDFs are PDF 1.2 format and higher (version number shows in Acrobat Reader under Document Summary) AND LZW-free, recreating them from the original document with Adobe Acrobat 3.0 (make sure it is set to Acrobat 3.0 format), Acrobat 4.0 or higher, Ghostscript 6 or later (always LZW-free), or other LZW-free PDF software if your PDFs are PDF 1.0 or PDF 1.1 (which always uses LZW). If using Acrobat, verify in the Preferences of Acrobat Distiller that it is set to use ZIP and/or JPEG compression instead of LZW. Many third-party products, including plug-ins, seem to generate non-LZW PDFs always, though you should check the documentation to verify, as some do support and use LZW compression instead of LZW-free Flate compression. To avoid this issue, you can use Ghostscript (and certain other software) which will always make LZW-free PDFs since Ghostscript 4 (Ghostscript 6 or higher strongly recommended due to Flate compression used on all elements, smaller files, better quality, better PDF support, and more).
Summary (see chart for much more detail):
Compression Utilities - Major formats of ZIP LZW, StuffIt 1.5.1, and
UNIX Compress have LZW-free replacements from approx 1993 and later
Graphics and PDF - GIF, TIFF LZW, and PDF LZW have official
replacements from 1996 and later
Postscript - printer drivers by Adobe, Apple, and Microsoft are surely
LZW-licensed and are free or included with your computer; for UNIX/Linux
users, you can use LZW-free Ghostscript (since version 4, 1996);
Ghostscript 6 [2000] or later recommended due to Postscript 3 support;
you also use Postscript 3 printers and drivers, which use no compression
or can optionally use Flate compression instead of LZW
Adobe Type 1 fonts - more research to be done on these
When I mention multiple platforms, I usually mean the software or files are compatible and useable on many types of computers, including Windows, Mac, Linux, UNIX, and sometimes others as well. The more types of computers a certain software or data file works on, the better choice it is, especially if you decide to switch to a different computer type in the future.
| File format using LZW | Alternative direct-replacement LZW-free Format | Comparison notes | Actions to take | Software that can use it or create it |
| PDF 1.0 or 1.1 (Acrobat 1.0, 2.0, and 2.1) | PDF 1.2 or higher (supported by Acrobat 3.0 format or higher)
supports use of Flate-compression, which can be a direct replacement for
LZW [September 1996 and later?] |
PDF 1.2 files support many more features and supports ZIP (Flate) compression in addition to LZW, while PDF 1.0 and 1.1 only support LZW. PDF 1.2 and higher files can contain LZW compressed items, but can also be LZW-free by using Flate instead. The PDFs must be created correctly to be LZW-free, especially with Acrobat 3. LZW-free PDFs can be read by Acrobat Reader 3 or higher, which is available even for really old computers. | Use Acrobat 3.0 (set to Acrobat 3.0 format), Acrobat 4.0 or
higher, Ghostscript 6 or higher (always LZW-free), or other software
(including any PDF plug-ins you use) that creates LZW-free PDF 1.2
or higher files to create new PDFs or to recreate your pre-PDF 1.2
files to PDF 1.2 to make them LZW-free; if using Acrobat, verify in the
Acrobat Distiller preferences that it is set to use ZIP and/or JPEG
compression instead of LZW
Open PDF file in Acrobat Reader then go to Document Summary to see what version of PDF it is |
Acrobat 3 (set to Acrobat 3.0 format) or Acrobat 4 or higher
to make PDFs
Acrobat Reader 3 or higher to read PDFs (Acrobat Reader 3 can even be used on Windows 3.1 and back to Mac System 7.0 on pre-PowerPC 68K CPUs) Ghostscript 6 [www.ghostscript.com] or higher (free; Feb 2000) has complete PDF 1.2 creation support on many platforms and never uses LZW GSView can view (and sometimes save as) PDF 1.2 or higher files on many platforms Other PDF reading and creation software exists for LZW-free PDF 1.2 or higher |
| GIF graphics format | PNG (approved Oct 1996) |
PNG uses lossless compression like GIF to preserve original quality; with anything larger than very small files (1K or less), PNG files are actually smaller than GIF; for photos or other continuous-tone graphics, JFIF (aka JPEG or .jpg), a lossy format, is still most appropriate for photos or other continuous tone graphics due to their very small size unless you need to preserve original top quality for uses like prepress applications, in which case you would use PNG or TIFF uncompressed | Use graphics software or conversion utilities to convert all your GIFs in your own collection, including those on websites you control, to PNG (for animated GIF replacement, use PNGs with website scripting like PHP; use Macromedia Flash, which uses a published format and can be created by third-party commercial or free software; use SVG [see www.w3.org/Graphics/SVG] which is open standard that matches and exceeds Macromedia Flash abilities, for which Adobe makes SVG Viewer; MNG is future possibility, but poor browser support currently) | Most all newer software can use PNGs and can be used to
convert GIFs to PNGs (GraphicConverter on Mac, PaintShop Pro for
Windows, and many others)
Can use PNGs: Microsoft Office 97/98 and newer |
| TIFF (LZW compressed version) graphics format | TIFFs (uncompressed) OR PNG (approved Oct 1996) [preferred] |
LZW-compressed TIFFs may not always be openable by other
programs such as AutoCAD 2000 or newer and can cause errors during the
RIP process used in prepress systems, so you should avoid using
especially if sending to a professional printer; TIFF LZW files also can
print slower than uncompressed TIFFs; PNG is a compressed format by default and has lossless compression like TIFF LZW to preserve original high quality, but actually makes smaller files than TIFF LZW; PNG is preferred if you do not have a specific reason to need TIFF |
Convert your LZW-compressed TIFFs to uncompressed TIFFs (which will make them larger) or PNGs (which will make them smaller) by resaving or converting your TIFFs in a graphics program or utility; if you use TIFFs for a critical application like prepress, use uncompressed TIFFs only until you can certify PNGs as performing properly throughout your entire production chain from desktop to final product | GraphicConverter on Mac, PaintShop Pro for Windows, and many
others; note that AutoCAD 2000 and later (among other programs) doesn’t support LZW-compressed TIFFs and instead supports PNGs and non-LZW TIFFs |
| ZIP archive files using LZW-based shrink compression (only used for small files zipped using PKZIP 1.1, or as default method in earlier versions) |
ZIP using Deflate (PKZIP 2.04g or later [Feb 1993]; see program notes) OR Zip using Implosion |
ZIP archives compressed using Deflate are smaller than either implosion (supported on PKZIP 1.1) or LZW-based shrink (supported on PKZIP 1.0 and 1.1) | Convert any remaining ancient shrink-compressed ZIP 1.x files by uncompressing and recompressing with program that creates ZIP 2.04g format archives using Deflate (see program notes) | ZIPs of all formats can be decompressed natively on Mac with
StuffIt Expander 5.5 or later at least (68K supported on Mac OS
7.5.3+) or Expander 4.x with the add-on "DropStuff with Expander
Enhancer" (Mac OS 6.0.5 or later), or PKUNZIP 2.04g or later on DOS or
Windows, Info-Zip, and others; If ZIP archive contains Mac apps or Mac-only files, you must use ZipIt [www.maczipit.com] or StuffIt Expander 6.5 (OS 8.1-9.x or OS X) because StuffIt Expander 5.5 won't work Decompress or compress using ZipIt Mac [www.maczipit.com], PKZIP 2.04g or later (DOS or Windows) [www.pkware.com], Info-ZIP 1.9 or later (UNIX, PC, and others), WinZip, and many other programs ZIP 2.04g is the most universal compressed archive format across virtually all platforms |
| UNIX compress (.Z) | Gzip [www.gzip.org] (.gz) [gzip 1.0.3 released Feb 2, 1993 as first major 1.x release, using .z file extension; gzip 1.1.1 in June 2, 1993 officially adopted the .gz extension] |
Like UNIX Compress (.Z), Gzip compresses one file only, so
you still use tar first to combine files together, then gzip the tar
file to compress it; Gzip can decompress .Z (UNIX compress) files and is intended to be a direct replacement for UNIX compress |
Convert all UNIX Compress (.Z) files by uncompressing with gzip, StuffIt Expander 6.5+ (or Expander Enhancer on 4.x and StuffIt Engine on 5.x), or other .Z capable uncompressor, and recompressing with gzip or ZIP 2.04g format (see ZIP section for programs) | Gzip can be decoded natively on Mac with StuffIt Expander 5.5
or later at least (68K supported on System 7.5.3+) or Expander 4.x with
the add-on "DropStuff with Expander Enhancer" (System 6.0.5 or later),
WinZip, MacGzip (PowerPC and 68K), Gzip for many platforms (see
www.gzip.org), and other programs
UNIX Compress .Z files can be decoded by gzip, free StuffIt Expander 6.5+ [www.aladdinsys.com] (Mac, Windows, Linux, Solaris), and other programs Gzip included in UNIX: Linux (1994 or later), HP-UX 10.x or
later (1995 or later), IRIX 6.2 or later (1996 or later), Solaris 8 or
later (2000 or later) |
| StuffIt 1.5.1 [.sit files] [1990 approx] (based on LZW-based UNIX Compress internally; chooses between LZW, Huffman, and RLE when compressing; traditionally Mac only) |
StuffIt 3.0 or later format [www.aladdinsys.com] (late 1992 or later) |
Both StuffIt 1.5.1 as well as public domain programs that use this format use LZW; StuffIt 3.0 format and later, which is a closed format, can only be created with StuffIt 3.0 or later software, and is LZW-free | Recommended: Convert StuffIt archives to open-source
multi-platform ZIP 2.04g format by decompressing with StuffIt Expander
(or other StuffIt program) and using ZipIt on Mac (in default Deflate
mode), StuffIt 5.5 or later, or ZIP programs on other platforms
If recompressing Mac apps or Mac-only files (ones have resource fork) using ZIP, you should use a Mac running ZipIt Mac (v1.4 and older works on older Macs too) or StuffIt 6.5 (Power Mac), since they support MacBinary OR Convert any StuffIt 1.5.1 archive to StuffIt 3.0 or later (use Mac if the archives contain Mac applications or very old Mac-only files unless you know what you are doing); StuffIt Lite 3.6 Mac which you can download has a feature to convert StuffIt 1.5.1 archives to StuffIt 3.0 format and will show you in lower left hand corner of window if the StuffIt file is 1.5.1 format; the StuffIt archive icon may also show "1.5.1" in the middle of the icon |
Decode StuffIt archives with StuffIt Expander (or full
StuffIt products) on Mac if they contain Mac apps or Mac-only files or
third-party programs if StuffIt 1.5.1 format and contain general
cross-platform data files
Decode ZIP archives with StuffIt Expander 5.5 (which works on 68K Macs) or later or ZipIt Mac [www.maczipit.com]. If ZIP archives contain Mac apps or Mac-only files, you must use ZipIt Mac (v1.4 works on old Macs too) or StuffIt Expander 6.5 (PowerPC OS 8.1-9.x or OS X; doesn't support 68K Macs), since they support automatic decoding of MacBinary Create ZIP archives with ZipIt Mac (default Deflate mode) [www.maczipit.com], StuffIt 5.5 or later, WinZip, PKZIP 2.04g or later, Info-Zip, or other ZIP programs Create archives with StuffIt 3.0 or later, including StuffIt Lite 3.6 which is still available for download as of 2002 [www.aladdinsys.com] |
| Adobe Postscript Level 2 [1990 introduced] (used on printers like HP LaserJet 4 [1993] and 5 series and newer, and possibly others); LaserWriter IIf and newer [1991], Personal LaserWriter NTR and newer [1992]; LaserWriter IINT, IINTX, and Personal LaserWriter NT, as well as the original LaserWriter and LaserWriter Plus have Postscript Level 1) |
Adobe Postscript 3 (only on Postscript drivers since 1998 and
newer printers) OR Ghostscript (free software for Windows, Mac, UNIX, Linux, etc; generates LZW-free Postscript-compatible files to substitute for any LZW compressed sections as needed) Note: Postscript Level 1 is LZW-free, but unsupported by newer drivers (Postscript driver on Mac OS X [2001], AdobePS 5 [1998] and higher for Windows and AdobePS 8.7 [2000] and higher on Mac OS 8.x/9.x), and printers with Postscript 1 often can't handle complex documents, such as newer complex PDFs and have limited or no memory expansion possibilities |
Adobe Postscript 3 supports use of Flate compression instead
of LZW so you can still generate compressed Postscript files without
use of LZW if you have a Postscript 3 device you will be printing them
to
Ghostscript generates uncompressed LZW-compatible Postscript for use with Postscript 2 devices, or Flate compressed Postscript for use with Postscript 3 devices (allowing you to generate and send a smaller amount of data) |
Not likely any change needed for Mac and Windows - if LZW
support included for use with Postscript 2, Apple, Adobe, Microsoft,
etc would have licensed it for the Postscript 2-compatible printer
drivers, as well as the manufacturers of any Postscript 2 compatible
printer you buy For Linux/UNIX, use Ghostscript, which is LZW-free and supports Postscript 3 on version 6 and later (Feb 2000) |
AdobePS Postscript drivers available for Mac and Windows 1998
and later that support Postscript Level 3 (download from www.adobe.com
in Downloads section)
Postscript 3 printer support included in Mac OS 8.1 and later [1998] (if using Mac OS 7.6.1, download LaserWriter 8.5.1 or 8.6 software from Apple) Ghostscript 6 or later [2000] which supports Postscript 3 (free software for Windows, Mac, UNIX, Linux); try version 5.5 (Sept 1998) if having trouble printing to Postscript 1 printers |
| DiskDoubler [.dd] (old Mac compressed format; files are individually compressed instead of grouped into an archive) |
ZIP 2.04g, gzip, or StuffIt 3 or later | uncompress with StuffIt Expander 6.5+ (or lower version with add-ons) or DiskDoubler itself; recompress in open-format ZIP 2.04g or gzip or closed-format StuffIt 3.0 or higher (see program notes above) | See program notes elsewhere in this chart | |
| ARC and PAK (old DOS compressed archive formats) |
ZIP 2.04g | uncompress with appropriate DOS or Windows utility and recompress with ZIP 2.04g-compatible program | See program notes elsewhere in this chart | |
| Adobe Type 1 fonts (Postscript fonts) | Needs more research If you use Mac or Windows and are using licensed fonts in-house, there should be no issues. Defer to other sources of advice if you are creating and/or distributing fonts. |
Macs have built-in capability to use them
Windows 2000, XP, and newer has built-in capability to use them. Older versions of Windows need Adobe ATM (such as Win 95/98/Me), which can be downloaded from Adobe |
Formats that DO NOT use LZW
Graphics, Bitmap - I recommend converting these bitmap graphics
listed here to PNG (if an old program can't use it, you can convert only
those needed, while keeping them all universally useable on newer
graphics programs and web browsers on many platforms)
PICT - Mac only graphics; RLE compression; vector or bitmap format
MacPaint (PNTG) - Mac only graphics; black and white bitmap format
BMP - Windows only graphics; no compression or RLE compression (for 4
or 8-bit graphics); bitmap format
Graphics, Vector (scalable line drawing) - I recommend converting
the other vector formats to EPS for universal useage among programs and
platforms
EPS/EPSF (Encapsulated Postscript) - multiplatform; vector format
(primarily, though you can insert bitmaps into it); no compression or
JPEG (lossy) compression
PICT - Mac only graphics; RLE compression; vector or bitmap format
WMF - Windows only graphics; no compression or RLE compression (for 4
or 8-bit graphics); vector format
EMF - Windows only graphics; vector format
Compressed Archives - these are so old, I would recommend converting
them to ZIP 2.04g archives anyways if you want to keep their contents
around by uncompressing the files then recompressing in ZIP 2.04g
format; see ZIP program notes in chart
CompactPro (.cpt) - Mac compressed archive; uncompress with any StuffIt
Expander
PackIt (.pit) - Mac compressed archive; uncompress with StuffIt Lite
3.6 which you can still download (see StuffIt section) or the real
PackIt program
ARJ - PC compressed archive
ZOO - PC compressed archive
LHA/LZH - PC compressed archive
Universal platform-neutral graphics formats - good formats to
use widely on many types of computers
PNG - good for compressed file size without loss of quality since it is
lossless; use for scanner output, web logos and pics, general
computer-made artwork, etc
JPEG - good for photos and other continuous tone where slight loss of
quality is OK (since it is lossy format) while getting very small file
sizes
EPS - good for graphic artist vector design (as in Adobe Illustrator)
and clip art; can scale up or down with no quality loss because it is a
vector format
TIFF uncompressed (there are PC byte order and Mac byte order versions,
but most software can read both) - use if need TIFF-specific features,
otherwise PNG offers same basic features with patent-free compression
GIF (uses LZW) - AVOID; obsoleted by PNG, limited to 256 colors, LZW
patented
Updated 2005-06-29