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The FamilySearch GEDZIP file format {#gedzip}

It is often useful to transmit a dataset together with a set of external files. The FamilySearch GEDZIP 7.0 file format is provided for this purpose. Version 7.0 was the first version of GEDZIP released; the version number of a GEDZIP file is the same as the version number of the dataset it contains.

A GEDZIP file is a zip archive, as defined by the .ZIP File Format Specification and standardized by ISO/IEC 21320-1:2015.

Each GEDZIP file contains the following entries:

  • An entry with name gedcom.ged containing a data stream.

  • An entry for each local file FILE structure in gedcom.ged, with the same zip file name as the corresponding FILE payload. If there is a local file named gedcom.ged, it must be renamed to a new unused filename with the same extension prior to constructing the GEDZIP.

All file names inside a GEDZIP are case-sensitive.

Many other zip-based file formats (such as jar, epub, docx, GEDCOM-X) assign special meaning to the zip directory META-INF and the zip file names MANIFEST.MF and META-INF/MANIFEST.MF. These have no special meaning in GEDZIP and it is recommended that they not be used in a GEDZIP file, both to avoid confusing systems that look inside zip archives to determine their file type, and to leave open the possibility of their addition in a future version of this specification.

When saved as a file, a GEDZIP should use the filename extension .gdz.

:::note A few details about the zip archive format are useful to fully understand GEDZIP:

  • An archive can contain 1 or more files.
  • Files within an archive can be added, removed, or updated individually without needing to re-process the rest of the archive. Libraries such as libzip allow applications to operate directly on the zip archive as if it were a normal directory tree.
  • What the zip specification calls a "file name" is actually a local path and may contain directories.
  • Directory separators are / internally and are converted to the appropriate form by the zip processing tool during zipping and unzipping. Because of this, unzipping a GEDZIP in any local directory results in all GEDZIP FILE references working as-is for the resulting gedcom.ged without the need for any additional processing. :::