How large can a DNA file be?
Researchers sometimes work with genome files of hundreds of gigabytes — your consumer export is 20–30 MB. The difference lies in what is actually measured, and it decides where your file can be analyzed.
Consumer files: compact by design
The export from MyHeritage, 23andMe, AncestryDNA or FamilyTreeDNA is a compressed text file — roughly 20–30 MB (smaller packed as .zip or .gz). It only contains genotypes at selected positions: typically 600,000–700,000 SNPs, one row per marker. It is a deliberately thin file — a genotyping chip measures known variants, not your whole genome.
Research files: a completely different scale
When researchers sequence a genome — for example ancient DNA from bone finds — they read every base in the genome, often several times over. Raw sequence files then grow to tens or hundreds of gigabytes. Such datasets are handled with specialist tools and server capacity; they are neither the format your provider export has, nor the format DNAHelper expects.
What the browser handles
Your consumer file is designed to be easy to compute on: parsing ~700,000 text rows and looking up markers against a trait database takes seconds in a modern browser — even on a phone. The limit is set not by your DNA data but by memory and file handling: practically speaking, files up to hundreds of megabytes work without problems, while multi-gigabyte files need other tools. And because the analysis is local you never wait for an upload — the file does not leave your device.
Size says nothing about content
A larger file does not mean a better result. What decides what DNAHelper can read is which markers the file contains — why a SNP can be missing is about chip coverage, not file size. And a small deletion error does not make the file "worse" — the raw file is a list of positions, nothing more.
Practical format questions
- Packed formats (
.zip,.gz) may need unpacking first — see the guide to .gz files. - Providers differ in separators and marker counts — file formats by provider.
- A file too large to open in a spreadsheet is often completely normal — do not open it in Excel, analyze it.
Also: What is a raw DNA file? · Unpack .gz files · Why is a SNP missing? · English overview