GEDCOM (English: GEnealogical Data COMmunication) is the specification of a data format that allows the exchange of data between different genealogy computer programs. It was developed by The Church of Jesus Christ of Latter-day Saints (Mormon Church), to support its members in genealogical research. Meanwhile, however, GEDCOM has established itself as the de facto standard and is supported by all popular genealogy programs as well as many genealogy websites on the Internet. The GEDCOM format (file extension:. ged) is text-based and contains the data of the individual persons of a family tree as well as information about their family relationships.

The specifications of a number of different versions of GEDCOM can be downloaded here (the documentation language is indicated by flag icons):

A very brief explanation of the GEDCOM format is given below. There is a lot of further information about GEDCOM on the internet. See for example

GEDCOM File Structure

A GEDCOM file is a sequential series of genealogical information (personal, family, source data ...), which are grouped in sets called records. The contents of a record are structured hierarchically in individual lines. Each line contains a hierarchical level (Level) and a unique identifier (tag), both of which contain information about the data in the line, followed by the actual data value. Relationships between individual data sets (parents, children, spouse ...) are represented by cross-reference pointers and cross-reference IDs (identifiers).

A new record always begins at the hierarchy level 0 with information about the record type, generally prefixed with a unique key phrase, enclosed between two "@" characters.

Example of the first line in an INDIVIDUAL record, i.e. a record containing information about a specific person
: 0 @I1@ INDI

The individual record consists of different data elements with a digit (level number) at the beginning of each line. The italicised text in brackets on the right below is explanatory, and does not form part of the line
: 1 NAME Peter John /Smith/    (Name)
  2 GIVN Peter John                 (Given name)
  2 SURN Smith                        (Surname)
  1 BIRT                                   (Birth: the following lines at the next level (2) contain details thereof)
  2 DATE 17 OCT 1937           (Date of birth)
  2 PLAC Smithfield Township, Monroe County, Pennsylvania, USA                  (Place of birth)

Links to other records are represented as follows
: 1 FAMC @F1@                       (cross reference to the family record of the parents)

The type indicators in the GEDCOM format are standardized and can be used only in the described form and structure. The GEDCOM standard does, however, allow the use of custom program-specific indicators. These must start with an underscore, e.g. "_UID"

Structures in GedTool

GedTool pools all similar records (personal, family, source data ...) together in an Excel worksheet. Every single record, for example concerning a person, forms a separate row in Excel. The respective indicators are mapped into the columns; there may be a number of lines in the header row due to multiple levels of hierarchy. The data values themselves are written in the appropriate cells (row of the person, column of the indicator). Multiply used indicators within a record are numbered internally (using hidden lines in the headings).