LZW

A lossless data compression algorithm that became widely adopted in graphics and document formats, most notably the TIFF (Tagged Image File Format) standard. Developed in 1984 by Terry Welch as an improvement on earlier Lempel–Ziv techniques, LZW enables digital files to reduce their size without losing any data. This makes it particularly valuable for applications where image fidelity or document accuracy is critical.

At its core, LZW works by identifying repeating patterns within data and replacing them with shorter codes stored in a dictionary. Unlike some other compression techniques, the dictionary is built dynamically during the encoding process, which allows the algorithm to adapt to the specific file being compressed. When the file is later decoded, the same dictionary is reconstructed, ensuring that the original data is perfectly restored.

The algorithm rose to prominence in the late 1980s and early 1990s due to its adoption in the GIF image format and TIFF files, both of which utilized LZW to make graphics more manageable in terms of storage and transmission. Although GIF became its most famous use case, TIFF was equally important in industries such as publishing, printing, and scanning, where high-quality image reproduction and cross-platform compatibility were crucial.

One of the defining moments in LZW’s history occurred in the 1990s, when patent disputes over its use sparked controversy, particularly in relation to GIF files. This led to the rise of alternative formats, such as PNG, which deliberately avoided LZW compression. Today, the LZW patent has expired, but the episode remains a pivotal example of how intellectual property rights can influence the adoption of technical standards.

Beyond TIFF, LZW has also been used in formats like PDF, PostScript, and other systems where efficient, lossless compression is required. While newer compression methods may outperform LZW in speed or file size reduction, its simplicity, reliability, and widespread support ensured that it became an enduring standard in digital imaging and document storage.