Downloaded a .gz file? How to prepare your raw data
One thing stops most FamilyTreeDNA users: the file is a .csv.gz, not a .zip. DNAHelper reads .gz directly in modern browsers — choose the file as-is, or unpack it first.
.gz is not .zip
Both are compressed formats but not interchangeable: .zip is a package that can hold several files (MyHeritage, 23andMe and Ancestry send .zip). .gz is stream compression of a single file — in FamilyTreeDNA's case a .csv. DNAHelper's file picker accepts .txt, .csv, .zip and .gz — .gz is unpacked locally in the browser. On older browsers: unpack the .gz first with the steps below.
Unpacking per platform
- Mac: double-click the file in Finder — Archive Utility unpacks it to
.csvin the same folder. - Windows: right-click → "Extract All" does not help for .gz — use 7-Zip (free) or open a terminal:
tar -xzf file.csv.gz. - Terminal (any):
gunzip file.csv.gzorgzip -d file.csv.gz. - iPhone/iPad: preferably unpack on a computer — .gz support in the Files app is uneven.
The Safari trap
Safari's "Open 'safe' files after downloading" setting automatically unpacks archives on download — so your .gz may already be a .csv by the time you find it in Downloads. That is actually helpful, but confusing if you are looking for the .gz name. If the unpacking seems to have gone wrong (empty or suspiciously small file): download again with the setting off, or use Chrome/Firefox.
Once the file is ready
Drop the .csv.gz (or .csv/.txt/.zip) straight into DNAHelper — parsing happens locally. Exactly what happens to the file. Guide for the download itself: FamilyTreeDNA.
Also: Check your file — free tool · File formats by provider · FTDNA guide · English overview