LZW Patent Expiration

By Deane Barker on June 9, 2003

Remember the big uproar back in the early days of the Web when Unisys started enforcing its patent of the LZW algorithm? This is the mathematical basis for the GIF image format. Unisys owned the patent since 1985, but only started enforcing it in 1996 when the Web took off.

This led to general gnashing of teeth, the creation of the PNG image format, and great sites like burnallgifs.com. It was one of the first “rally-‘round-the-flag” issues on the Web after I first logged on in 1995.

Well, in case you missed it, the patent to LZW expires on June 20, and Unisys has said they’re not renewing it. They’ll enforce it up until the end (it goes a year longer overseas and some variations on the algorithm have patents for another 20 years), but then they’ll let it go. CNet has an interesting article about how this may doom the PNG image format.