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Pack200, specified in JSR 200[1] (J2SE 1.5), deprecated in JEP 336[2] (Java SE 11) and removed in JEP 367 (Java SE 14),[3] was a compacting archive format developed by Sun, capable of reducing JAR file sizes by a factor of 7 to 9. Pack200 was optimized for compressing JAR archive files, specifically the Java bytecode portion of the JAR files. Applications of this technology included faster Java application deployment over Java Web Start.

After Pack200, usually a gzip compression was applied. In HTTP compression, such content was specified by the Content-Encoding type "pack200-gzip". When stored as a file, the extension ".pack.gz" was used.

Pack200 may have also referred to the Pack200 compression tools (pack200 and unpack200) provided in Sun's Java Development Kit since Java 5, as well as the Pack200 compressed files.

External links[edit]


  1. ^ "JSR 200: Network Transfer Format for Java Archives". Retrieved 2014-06-09.
  2. ^ "JEP 336: Deprecate the Pack200 Tools and API". Retrieved 2018-11-10.
  3. ^ "JEP 367: Remove the Pack200 Tools and API". Retrieved 2020-06-02.