DeflateZIP

DeflateZIP is a non-formal term used to describe the common practice of storing data in a ZIP archive with the Deflate compression method applied to each file entry. It is not a separate file format, but a usage pattern within the ZIP container.

Deflate is a lossless compression algorithm that uses LZ77 matching followed by Huffman coding. In ZIP archives, the Deflate method (often identified as method 8) compresses individual entries, enabling relatively fast compression and random-access extraction of files.

A DeflateZIP archive includes per-entry compressed data plus a local file header for each entry, and a central directory at the end that records metadata and CRC checksums. Some tools also use optional data descriptors. Encryption, when available, is a separate feature and not inherent to the Deflate algorithm itself.

Advantages of DeflateZIP include broad compatibility across operating systems and software, a favorable balance of compression speed and ratio for many data types, and support for random access to individual files without decompressing the entire archive.

Limitations and considerations include reduced effectiveness on already compressed data, potential risk of data corruption if the archive's central directory is damaged, and occasional compatibility quirks among older or less capable tools. Some ZIP tools also provide Deflate64 (method 9), which offers a larger dictionary and different performance characteristics but is not universally supported.

See also: Deflate; ZIP (file format); Deflate64; zlib.