---
title: Which of your custom tags each site will delete
slug: what-each-site-deletes-from-your-gedcom
description: Six destinations, one instrumented file, one table. Which underscore tags survive, which become notes, and which are gone with no message.
tools: [gedcom-dialect-report, inspect]
difficulty: intermediate
time: 20 minutes
lastChecked: 2026-09-03
published: 2026-09-03T10:25:00+02:00
---

# Which of your custom tags each site will delete

You are about to move a tree. The question is not whether the people arrive. They will. The question is whether the source links, the media metadata and the relationship qualifiers arrive with them, and no destination publishes that list.

FamilySearch comes closest. Its help centre page on [what happens to information uploaded from a GEDCOM file](https://www.familysearch.org/en/help/helpcenter/article/what-happens-to-information-uploaded-from-a-gedcom-file) says the sources, notes and media in a GEDCOM cannot be transferred to Family Tree, which is honest and states a category. It names no tag, and it is the platform's own statement about the platform, so read it first and read the tag counts below it. MyHeritage publishes a page about photos. Ancestry publishes nothing found in a September 2026 search. The two independent references the experts cite for this, `gedcomassessment.com` and `genealogytools.com`, both fail DNS.

So the tags have to be counted in the file, and the destination rules read off a knowledge base with a date on every line.

## What causes it

A GEDCOM tag beginning with an underscore is not in the specification. Every program is free to invent them and every program does. An importer that meets `_APID` has three options: map it to something of its own, keep it as text, or drop it. Only the first keeps the meaning, and only the exporting program knows what the meaning was.

Two tags carry most of the value in a moved tree.

`_APID` sits under a source citation in an Ancestry export. Its value looks like `1,60525::120334455`: a database id and a record id inside Ancestry's own collections. It is the link from your citation to the scanned page. Ancestry re-links it on upload. RootsMagic ignores it. Gedcom Publisher maps it to a RecordID.

`_UID` is a per-record identifier that lets two programs recognise the same person after a round trip. Ancestry imports `_UID` and exports it as `UID` with no underscore, cut to 32 hex digits. RootsMagic reads a 36-character PAF-style value and rejects a bare `UID` as unknown. Family Historian writes it wrapped in braces.

The rest of an export's underscore tags are photo crop boxes, tree ids, server environment names and to-do flags. Losing them costs nothing. Losing `_APID` costs every link back to a record image.

```mermaid
flowchart TD
  E["Your export"] --> T{"Is the tag in the specification?"}
  T -- "yes: INDI, FAM, NAME, DATE" --> K["Arrives at every destination"]
  T -- "yes, but attached: SOUR, NOTE, OBJE" --> A{"Read the destination card"}
  T -- "no, underscore tag" --> U{"Whose tag is it?"}
  U -- "the destination's own, going home" --> H["Re-linked. Only _APID into Ancestry"]
  U -- "any other program's" --> X["Dropped, or turned into note text"]
  A -- "FamilySearch" --> X
  A -- "Ancestry" --> M["Notes and sources arrive, media does not"]
  A -- "GEDmatch" --> X
```

## What the six destinations do

Numbers below come from one run of Dialect Report on `fixtures/public/ancestry-export-synthetic.ged`, a 1,849-byte Ancestry-shaped file holding 3 people, 11 distinct custom tags across 16 lines, 3 NOTE, 7 SOUR and 2 OBJE lines. Reproduce them by dropping that file on [Dialect Report](/gedcom-dialect-report).

| Destination | Custom tags | Notes, sources, media | The rule that fired |
|---|---|---|---|
| FamilySearch Family Tree | 11 tags, 16 lines dropped | 3 NOTE, 7 SOUR, 2 OBJE dropped | `familysearch.custom-lost`, `familysearch.notes-sources-media` |
| Ancestry.com | 9 tags, 9 lines assumed lost. 4 `_APID` re-link | 2 OBJE dropped, media files not uploaded | `ancestry.custom-unverified`, `ancestry.apid-relinks`, `ancestry.media-excluded` |
| MyHeritage | 11 tags, 16 lines: the wizard offers Convert to Notes or discard | 1 custom `EVEN`/`TYPE` event round-trips | `myheritage.unknown-tags`, `myheritage.custom-events` |
| Gramps 6.0 | 8 nested lines become text in a note; 2 header lines (`_ENV`, `_TREE`) dropped | 3 NOTE lines re-wrapped with CONC at 72 columns | `gramps.nested-custom`, `gramps.head-custom`, `gramps.notes-rewrap` |
| WikiTree | 11 tags, 16 lines not mapped to profile fields | reviewed one profile at a time in GEDCOMpare | `wikitree.custom-tags`, `wikitree.gedcompare` |
| GEDmatch | 11 tags, 16 lines plus all 12 NOTE, SOUR and OBJE lines: assume dropped | no statement published, so assume dropped | `gedmatch.custom-dropped`, `gedmatch.public` |

One row in that table is different from the other five. Ancestry is the only destination that does anything with `_APID` other than drop it, and only because `_APID` is Ancestry's own tag going home. Move the same file to any of the other five and those four citation links become nothing. No message is shown.

Read the whole card, not the tag column. `familysearch.no-export` says Family Tree has no GEDCOM export at all, so a tree copied in cannot come back out as a file, and `gedmatch.public` says every uploaded tree is public.

For the one program with a maintained per-tag reference, use the reference. The [Family Historian GEDCOM Extension List at fhug.org.uk](https://www.fhug.org.uk/kb/kb-article/gedcom-extension-list/) documents every `_` tag Family Historian writes and says for each whether other software ignores it. Nothing written here improves on that for that program.

## The run

1. Open [File Inspector](/inspect) and drop your file. Read **Header** to confirm the producing program. A file that says `Ancestry.com Family Trees` under Source will carry `_APID`; one that says `MyHeritage` will carry `_UID` as 32 hex digits.
2. Open [Dialect Report](/gedcom-dialect-report) and drop the same file. The header line states the knowledge base version, `2026-09-02` at the time of writing.
3. Read **Producer**. On the fixture it reads `Ancestry.com Member Trees (98%)`, with the rationale listing `HEAD.SOUR Ancestry.com Family Trees (Ancestry.com Member Trees) matches "ancestry"` and `signature tags present: _APID, _TREE, _ENV`.
4. Read **File facts** on the right. Custom tags reads `11 distinct, 16 lines` on the fixture.
5. Read **Custom tag inventory**. One row per tag, with Kind, Count, First at, Carried by, Under and Sample values. `_APID` reads `extension`, count 4, carried by `INDI 3, FAM 1`, under `INDI.SOUR, FAM.SOUR`. `UID` reads `not in spec`, count 3, carried by `INDI 3`, under `INDI`.
![The Custom tag inventory in Dialect Report on the Ancestry fixture: _APID with count 4 under INDI.SOUR and FAM.SOUR, UID with count 3 under INDI.](/kb/shots/what-each-site-deletes-from-your-gedcom-inventory.jpg)
6. Scroll to **Destination compatibility**. Six cards, one per destination. Each warning carries a badge reading `dropped`, `rewritten`, `limit` or `note`, a rule id, a confidence and a checked date.
7. Read the card for the site you are moving to. Copy the rule id if you want to cite it later; every rule links its own sources.
![The Destination compatibility cards: FamilySearch, Ancestry, MyHeritage and Gramps, each listing its dropped and rewritten counts with rule ids and dates.](/kb/shots/what-each-site-deletes-from-your-gedcom-destinations.jpg)
8. Decide before uploading. If a card says a tag family is dropped and that family holds your citation links, export a second copy of the tree and keep it. There is no way to get the tags back from the destination.

## What to check when it worked

- **Producer** names the program you exported from, at 90% or better. A lower number means the header was rebuilt by something in between, and the tag predictions are weaker.
- **Custom tag inventory** row count equals the Custom tags figure in File facts. On the fixture both read 11.
- Every warning on the destination card carries a rule id and a checked date. A line with no date is not a claim this site makes.
- The counts add up. On the fixture the GEDmatch card's `gedmatch.custom-dropped` line reads `11 custom tags (16 lines) plus 3 NOTE, 7 SOUR and 2 OBJE lines`, and that 11 and 16 are the pair File facts states.

## What to do when it did not

**Producer reads `unknown`.** The file has no `HEAD.SOUR` this knowledge base recognises and no signature tags. The destination cards still apply, because they key off tags rather than producers, but the producer quirks section will be empty.

**A tag you care about is not in the inventory.** The inventory lists tags outside the specification. A standard tag such as `SOUR` or `OBJE` is counted in File facts instead, and its fate is on the destination cards under notes, sources and media.

**The destination you want is not one of the six.** No card, no claim. Read the **Custom tag inventory** and treat every extension tag as lost, which is what five of the six do.

**You want the tags back after the move.** They do not come back. FamilySearch has no GEDCOM export. Ancestry exports 5.5.1 with its own tags, not yours. Keep the original file.

## Related

- Pillar: [how to prepare a GEDCOM for Ancestry, MyHeritage, FamilySearch or GEDmatch](/how-to/prepare-a-gedcom-for-ancestry-myheritage-familysearch-gedmatch)
- Sibling: [how to prepare a GEDCOM for GEDmatch](/how-to/prepare-a-gedcom-for-gedmatch)
- [How to remove living people before sharing your family tree](/how-to/remove-living-people-before-sharing-your-family-tree)
- [How to convert GEDCOM 5.5.1 to 7.0, and what does not survive](/how-to/convert-gedcom-5-5-1-to-7-0-and-what-does-not-survive)