GED-VIEW opens six kinds of family file and writes every one of them: GEDCOM as 5.5.1 or 7 (older versions are read but not written), GEDZIP, a zip with a media folder, GEDCOM X, Gramps XML and Gramps CSV. They do not carry the same things. This page says what each holds, what comes back unchanged after a round trip, and which to choose. The tool is Tools > Convert; the conversion guide covers the page itself.

Every type at a glance

GEDCOM (.ged)
The plain text file every genealogy program trades. Read from version 5.3 onward, written as 5.5.1 or 7. Photos are file names only.
GEDZIP (.gdz)
A zip with the tree as gedcom.ged in GEDCOM 7 and the media packed beside it. Programs that read GEDCOM 5.5.1 do not open .gdz archives; choose the zip with a media folder for them.
Zip with a media folder (.zip)
The same package for older programs and for people: family.ged in the version you choose, next to a media folder.
GEDCOM X (.json or .xml)
FamilySearch's exchange model, used by its API and a few developer tools rather than by family programs. Not a version of GEDCOM.
Gramps XML (.gramps)
The archive format of Gramps, compressed. Gramps opens it directly; more survives than through any GEDCOM.
Gramps CSV (.csv)
A spreadsheet in four sections that Gramps imports. People and families only; good for adding people to an existing tree.

What survives a round trip

A round trip is writing the file in a type and reading it back; the counts on the Overview page show how it went. What stays exact, type by type:

GEDCOM, GEDZIP and the zip
Everything: people, families, events, sources, media, notes, repositories and submitters.
Gramps XML
People, families, events, sources, media and repositories. Every note written inside a record comes back as a note record of its own, and the file's researcher becomes its one submitter.
GEDCOM X
People, families and events. Notes stay on the records that carry them, but shared note records and repositories have no place of their own, and citations written as text and media files come back as source descriptions.
Gramps CSV
People and families. Everything else has no column.

GEDCOM X

GEDCOM X is not a version of GEDCOM. When a GEDCOM X file is opened here, its people, families and sources are read back into GEDCOM records that follow the 5.5.1 rules. Before writing one, the Convert page lists its other limits: GEDCOM X has its own model, so associations, aliases, submissions, the header, custom tags, LDS ordinances and event agencies are dropped and listed; a family with only one parent has no couple, so the parent keeps the children but the family's own events are dropped; shared notes are written into every record that uses them and are separate notes again on the way back. JSON and XML hold the same content; choose JSON unless the program asks for XML.

Gramps XML and Gramps CSV

Gramps XML keeps nearly everything. The two exceptions the Convert page names: Gramps has no place for LDS ordinances, submission records, most of the file header and custom program tags; those are listed in the report. And each distinct place text becomes one Gramps place, as it is written, without splitting it into town, county and country.

Gramps CSV is four tables in one file (Place, Person, Marriage, Family) with record IDs in square brackets. It carries names, sex, birth, baptism, death and burial with their date, place and source title, the death cause, one occupation, one residence, one attribute and one note per person, marriages, children and places. Every other event, note, source detail, media file and custom tag has no column and is listed in the report.

Which one to choose

A program that reads GEDCOM 5.5.1
Plain GEDCOM 5.5.1, or the zip with a media folder when the photos should come along.
A program that reads GEDCOM 7
GEDCOM 7, or GEDZIP with the media included.
A relative
Plain GEDCOM 5.5.1 opens everywhere, GED-VIEW included; add the zip with a media folder for the photos.
Gramps
Gramps XML for a new tree; Gramps CSV to add people to one that exists.
Software built on FamilySearch's model
GEDCOM X, as JSON unless XML is asked for.
A copy to keep
GEDZIP when the photos matter: the tree and its media in one file that any zip tool can open.

Next

Open the file, open Convert and keep this page beside the Format dropdown. Pick the type the receiving program names in its own import dialog; when it names none, plain GEDCOM 5.5.1 is the one that opens everywhere.