GEDCOM Data Quality & Cleanup
Finding and fixing broken links, impossible dates, and duplicate individuals hiding in a GEDCOM file — before you import it anywhere or share it with family.
A GEDCOM file can be perfectly valid as a file and still be wrong as a family tree. Nothing in the format prevents a person from dying before they were born, or a family record from listing a child that no longer exists. Genealogy software mostly tolerates this quietly; importers on other platforms usually do not, which is why a tree that has looked fine for years can fail the moment you try to move it.
Three problems account for most of it. A dangling reference points at a record ID — @I417@ — that is not defined anywhere in the file, typically left behind when someone was deleted without the pointers to them being cleaned up. A one-way link records a relationship from one side only: a child names its family in a FAMC line, but that family's CHIL list never names the child back, so the two disagree about who belongs to whom. And impossible dates are internal contradictions — a death before a birth, a parent born after their own child, a marriage after both parties had died.
None of these require guesswork to find, because each is a mechanical contradiction the file states about itself. The guides in this section explain what each problem looks like in the raw text, why it usually appears, and which ones matter enough to fix before an import. Duplicates are the exception: they are a judgement call rather than a contradiction, and are worth handling deliberately rather than in bulk.
Start hereGEDCOM ValidatorCheck a file for all three problems at once and get the line number of every issue, so you can find it in the raw text or in your genealogy software and fix it at the source.6 guides in this section
- Cleaning Up a GEDCOM Inherited From a RelativeInherited a GEDCOM file from a relative's old software? Here's a step-by-step workflow for checking, cleaning, and trusting it before you build on it.
- Duplicate Individuals: How They Happen and How to Find ThemDuplicate people are the hardest GEDCOM problem to catch automatically, because the file gives no way to prove it. Here is a workflow that finds them anyway.
- Finding and Fixing Impossible Dates in Your Family TreeDeath before birth, 200-year lifespans, a parent younger than their child — how impossible dates get into a GEDCOM file, and how to track them all down.
- How to Fix Broken Family Links in a GEDCOM FileA broken family link means a GEDCOM pointer only goes one way. Here's how that happens, how to spot it, and how to fix it in your file without losing data.
- How to Validate a GEDCOM File Before Importing It AnywhereA pre-import checklist for GEDCOM files: what to check, in what order, and which free tool handles each step — so the import fails on your screen, not theirs.
- What a "Dangling Reference" Error Actually Means (and How to Fix It)A dangling reference means a GEDCOM pointer leads to a record that no longer exists anywhere in the file. Here's why that happens and how to track it down.