--- title: How to prepare a GEDCOM for GEDmatch slug: prepare-a-gedcom-for-gedmatch description: Every GEDmatch tree is public. Redact the living, cut the branch you mean to share, and check the file for addresses left in free text. tools: [living-person-privatiser, subtree-extractor, gedcom-dialect-report] difficulty: intermediate time: 25 minutes lastChecked: 2026-09-03 published: 2026-09-03T10:35:00+02:00 --- # How to prepare a GEDCOM for GEDmatch GEDmatch trees are public. Not private-by-default, not visible to matches only. Anyone with an account reads the names, dates, places and relationships in the file you upload. The best answer currently on the first page of results for this is to open the file and rename every living person to "Private" by hand. On a 20-person tree that is twenty edits. On a 4,000-person tree it is a weekend, and the names are only the first of four places a living person leaks. ## What causes the exposure GEDmatch marks people it believes are living as `LIVING` and hides their details. Two things make that unreliable as your only protection. The rule it uses is a guess from the file. A person with a birth date and no death record is treated as possibly living. A person with neither is a coin toss. The GEDmatch forums carry threads from people whose living relatives showed in full because a birth year was missing, and threads from people whose dead ancestors were hidden because a death date was. The second is that a name is not the only identifier. A phone number in a NOTE, a street address under `RESI`, an email in a source citation and a file path holding a person's name in an `OBJE` line all survive the name being replaced. Nothing on the GEDmatch side reads those fields for you. Two decisions come before the upload: who counts as living, and how much of the tree GEDmatch needs at all. GEDmatch matches DNA to a lineage. A branch is usually enough, and a branch you cut yourself carries a fraction of the exposure. ```mermaid flowchart TD S["A tree you want on GEDmatch"] --> D{"Does GEDmatch need the whole tree?"} D -- "no, one line of descent" --> X["Subtree Extractor: cut the branch first"] D -- "yes" --> P["Living Person Privatiser"] X --> P P --> C{"Read Identifiers in free text"} C -- "rows listed" --> F["Turn on the free-text scan and rebuild"] C -- "none" --> B["Build the privatised file"] F --> B B --> R["Dialect Report: read the GEDmatch card before uploading"] ``` ## The run Numbers below are from `fixtures/public/Musterstammbaum.ged`, a 20-person Ahnenblatt export. 1. Open [Subtree Extractor](/subtree-extractor) and drop the file. The header line reads `20 people in 34 records`. 2. Under **Root person**, use the **Person** select to pick whoever the DNA test belongs to. On this fixture that is `@1@ Max Mustermann, b. 1 JAN 1980`. The **Search** box beside it filters by name, xref or year. 3. Under **Walk**, set **Direction** to `Ancestors and descendants`, **Generations up** to 2 and **Generations down** to 0. That gives the ancestry GEDmatch matches against, without the living descendants. 4. Read **These settings include**. With those settings the fixture reports `13 records of 34`, `7 people`, `3 families`, `1 sources, notes, media` and `3.1 K characters`, then `1 root 6 ancestors` below. That is 7 of 20 people leaving your machine instead of 20. 5. Read **Dropped so nothing points outside**. It reads `3 to FAM records`, and the table names them: `FAMS @F10@` at line 30, `FAMS @F7@` at line 80 and `FAMC @F4@` at line 109, each `FAM record left out by these settings`. The extract holds no pointer to a record it does not carry. 6. Press the primary button, which reads **Extract 13 records** with those settings, and keep the file. 7. Open [Living Person Privatiser](/living-person-privatiser) and drop your file. The header line states the split. On the full fixture it reads `20 people. 11 are treated as living and will be redacted; 9 are dead`, with `Cutoff year 1926`. 8. Read **How each verdict was reached**. On this fixture 8 people were decided by a death record and 12 by the birth cutoff. A file where a large share sits under `nothing to go on, treated as living` is a file whose dates are thin, and the redaction will be broad. ![The Living Person Privatiser on Musterstammbaum.ged: 11 of 20 people treated as living at a 1926 cutoff, the verdict table crediting 8 to death evidence and 12 to the birth cutoff, and the settings panel below.](/kb/shots/prepare-a-gedcom-for-gedmatch-privatiser.jpg) 9. In **Settings**, leave **Scan free text for identifiers** ticked. Untick **Keep the surname** if the surname alone identifies the family in a small place. 10. Read **Identifiers in free text**. On this fixture the scan finds none. On `fixtures/public/TGC551.ged` the same scan finds 26 across the header and the records: 2 street addresses, 10 phone numbers, 6 emails, 2 national identifiers and 6 leaked names. The line above the table states how many sit outside the records being redacted, which is the number field-level redaction would leave behind. 11. Press **Build the privatised file**, then use the download link. Press **Download classification CSV** as well if you want the per-person verdict as a spreadsheet. 12. Open [Dialect Report](/gedcom-dialect-report) and drop the privatised file. Read the GEDmatch card under **Destination compatibility**. 13. Check the `gedmatch.auto-living` line. On the unprivatised fixture it reads `12 people have a birth date and no death record; GEDmatch may replace their name and dates with LIVING`. On the privatised file that count should fall, because those people no longer carry a bare birth date. ![The WikiTree and GEDmatch cards in Dialect Report: GEDmatch noting every uploaded tree is public, rewriting 12 people with a birth date and no death record to LIVING, and dropping 7 custom tags plus 21 SOUR lines.](/kb/shots/prepare-a-gedcom-for-gedmatch-dialect.jpg) 14. Read `gedmatch.extension`: the file name must end in `.ged`. ## What to check when it worked - The privatised file, opened in [GEDCOM Viewer](/gedcom-viewer), shows no given name for anyone you meant to redact. Search the surname of a living relative and read the row. - **Identifiers in free text** on the privatised file reports no address, phone number, email, national identifier or leaked name. - The GEDmatch card's `gedmatch.custom-dropped` count tells you what will not be shown at all. On the fixture that is 7 custom tags across 26 lines plus 21 SOUR lines. - The subtree file holds only the people you chose. Its **These settings include** count is the number of people GEDmatch will publish. - The file name ends `.ged`. ## What to do when it did not **Someone living was left in the clear.** They had no birth date and no death record, so nothing placed them. Set **People with nothing to go on** to `treated as living` and rebuild. The person table's `unknown` filter lists exactly who that affects. **Someone long dead was redacted.** Their death is recorded as `DEAT Y` with no date, which the cutoff cannot use. Add a death year to the record and run again. The GEDmatch card carries a matching warning, `gedmatch.deat-y`, on files that hold those records. **The privatised file is larger than the original.** Redaction writes a determination on each record saying which rule fired, so the decision travels with the file instead of living in this browser. Untick **Write each verdict into the file** if you would rather not carry it. **You want the full tree on GEDmatch anyway.** Then read the whole GEDmatch card, not the auto-living line alone. It publishes no list of supported tags, so [which of your custom tags each site will delete](/how-to/what-each-site-deletes-from-your-gedcom) treats every extension tag as dropped. ## Related - Pillar: [how to prepare a GEDCOM for Ancestry, MyHeritage, FamilySearch or GEDmatch](/how-to/prepare-a-gedcom-for-ancestry-myheritage-familysearch-gedmatch) - Sibling: [which of your custom tags each site will delete](/how-to/what-each-site-deletes-from-your-gedcom) - [How to remove living people before sharing your family tree](/how-to/remove-living-people-before-sharing-your-family-tree) - [How to split one branch out of a large family tree](/how-to/split-one-branch-out-of-a-large-family-tree)