---
title: How to prepare a GEDCOM for GEDmatch
slug: prepare-a-gedcom-for-gedmatch
description: Prepare the branch you intend to share, redact living people's details, review privacy limits, and validate the file before a GEDmatch upload.
tools: [living-person-privatiser, subtree-extractor, gedcom-dialect-report]
difficulty: intermediate
time: 25 minutes
lastChecked: 2026-09-06
published: 2026-09-03T10:35:00+02:00
---

# How to prepare a GEDCOM for GEDmatch

Treat a GEDmatch upload as disclosure beyond your own computer. The toolkit's `2026-09-02` destination profile warns of public tree visibility. Check GEDmatch's current upload terms and audience before sending a tree; this article's 6 September tool check did not include a fresh GEDmatch upload or policy verification.

Keep an untouched backup and prepare a separate sharing copy. Renaming living people to `Private` does not remove their dates, addresses or names in notes, sources and media paths.

## What causes the exposure

Do not rely on a destination's living-person filter as your only protection.

The Dialect Report profile flags people with a birth date and no `DEAT` structure as a possible `LIVING` conversion risk. That count comes from the local file. It does not reproduce GEDmatch's current algorithm or establish what happens to people with missing dates.

A phone number in a `NOTE`, a street address under `RESI`, an email in a citation or a media path can identify someone after you replace their name. Remove private content before uploading. A profile prediction that GEDmatch may ignore a field does not mean the service never receives or retains it.

Decide who counts as living and how much of the tree you intend to share. A smaller ancestor branch can support your research without disclosing unrelated branches. Extraction still retains the root and can carry private text from sources and header notes.

```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 --> V["Resolve verification failures and inspect the downloaded copy"]
  V --> R["Read the GEDmatch profile and current upload requirements"]
  R --> FMT["Convert only if required, then validate the final download"]
  FMT --> TEST["Test with synthetic or deceased-only data before the main upload"]
```

## The run

The screenshots show `fixtures/public/Musterstammbaum.ged`, a 20-person Ahnenblatt example. Follow the counts and warnings for your own file; the classifier's date cutoff changes with time.

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**, choose `Ancestors`, set **Generations up** to your intended depth and leave **Spouses** and **Siblings** off unless you want those relatives too. Both options start off. An ancestor-only extract still includes its root, who may be living.
4. Read **These settings include** and inspect the people you intend to share. No file leaves your machine through this tool; you choose whether to upload its download later.
5. Read **Dropped so nothing points outside** and **Header the extract will carry**. The extractor removes parsed pointers outside its record set, but retained notes and citations can name excluded people. The header includes the root name and source filename.
6. Press **Extract N records** and keep the downloaded copy. Read encoding or ledger warnings, then load that download into the next tool.
7. Open [Living Person Privatiser](/living-person-privatiser) on the extract. Read the living/dead split and the cutoff year. Do not switch back to the unextracted original by mistake.
8. Read **How each verdict was reached** and review known living people plus the **no evidence** group. Leave **People with nothing to go on** set to `treated as living` unless you have evidence to change it.
![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. **Keep the surname** starts checked. Untick it unless you intend to disclose those surnames. Keep dates removed, personal events dropped, and place, note, media, family-event and free-text protections enabled. See [the full privacy workflow](/how-to/remove-living-people-before-sharing-your-family-tree).
10. Read **Identifiers in free text**, including hits outside redacted person records. The scanner uses supported patterns and can miss aliases, unusual identifier formats and indirect identification through family links.
11. Press **Build the privatised file**. Resolve `Verify: fail` before sharing. A pass means the configured scan found no residuals; it does not prove anonymity. Click **Download privatised .ged** and inspect it. Keep **Download classification CSV** private because it contains original names and rationales.
12. Open [Dialect Report](/gedcom-dialect-report) and drop the privatised file. Read the GEDmatch card under **Destination compatibility**.
13. Read `gedmatch.auto-living` as a local risk count, not a privacy test. Redaction can reduce this count by removing birth dates without changing the visibility of the retained person records. Read the rule's confidence and sources.
![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. Use a `.ged` filename and check current upload requirements. If a version conversion is necessary, review its losses, then validate the final download with [GEDCOM Validator](/gedcom-validator). Test a synthetic or deceased-only branch on GEDmatch before uploading your main sharing copy.

## 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.
- The build reports `Verify: pass.` and you have reviewed names, aliases, notes, source text, paths, header details and retained relationships in the download.
- You have accepted the risks listed in `gedmatch.custom-dropped`. That low-confidence profile warning predicts possible loss; it does not establish deletion or confidentiality.
- The subtree file holds the intended people. Its local count does not predict how many people GEDmatch will display.
- GEDCOM Validator reports no unexplained errors in the final file, and your test import matches the relationships and visibility you intended.
- The file name ends `.ged`.

## What to do when it did not

**Someone living was left in the clear.** Check that person's Rule and rationale. A wrong death event, old birth year, relative inference or changed batch setting can cause this. Use the **no evidence** filter for the batch group and leave it `treated as living`. Correct source-supported errors and review known living people after rebuilding.

**Someone long dead was redacted.** Read the classifier's rationale before changing anything. Our privatiser accepts `DEAT Y` without a date as death evidence, unless an earlier privacy flag takes precedence. The destination warning `gedmatch.deat-y` comes from a single dated report about GEDmatch and does not describe our classifier. Do not invent a death year to satisfy an importer.

**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.** Review the entire sharing copy and confirm the current visibility terms first. The profile has low-confidence assumptions about unsupported tags. Read [how to assess possible custom-tag losses](/how-to/what-each-site-deletes-from-your-gedcom) and keep your original file and media.

## 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)