Analyze 23andMe Raw Data Privately on Your Computer

You can analyze a downloaded 23andMe raw-data file on your own computer. BioDecode reads supported records from the file and compares them with a local ClinVar database. This guide walks through the file, setup, and report so you can decide whether that workflow fits your needs. It is educational variant annotation, not a replacement for a clinical test or 23andMe's own reports.

What the 23andMe raw data file actually is

Your results come from a genotyping array, not whole-genome sequencing. The set of positions depends on the chip version used for your test. A consumer array reads selected positions across the genome. That is a fraction of one percent of your ~3 billion base pairs. Positions outside that set are not assessed by this file.

The download is a plain-text, tab-separated file, delivered zipped with a name that starts with genome. Past the header comments, every line is one marker with four columns:

• rsid — the marker's identifier, usually a dbSNP rs number
• chromosome
• position — the base-pair location, on the GRCh37 / build 37 reference
• genotype — the reported call, such as AG; some positions have a single-base call or a no-call

So rs429358 19 45411941 CT means "at marker rs429358 on chromosome 19, you carry one C and one T." What a marker means comes from cross-referencing it against a database — the file itself only records letters and positions.

How to download your raw data

1. Sign in at 23andme.com and click your profile name (top right).
2. Open Resources → Browse Raw Genotyping Data, then choose Download. The alternate path is Account Settings → 23andMe Data.
3. Confirm the date of birth on the profile, read the notice, tick the box, and submit the request.
4. 23andMe emails you when the file is ready — currently described by its support page as usually about one week, sometimes up to 30 days. Check the provider's current notice when requesting it.
5. Find the genome*.zip in your downloads and unzip it. Keep it somewhere you control.

That last step matters more than it sounds. The moment the file leaves 23andMe's servers, protecting it is on you. Before you hand it to the next service, it's worth reading whether it's safe to upload your DNA at all.

Reading it for health-relevant variants

The question most people actually have is whether any of their markers are flagged in ClinVar, the NIH's public archive of variant–condition relationships. ClinVar records whether a variant has been classified as benign, uncertain, likely pathogenic, or pathogenic, and how much expert review stands behind that call.

Matching your file against ClinVar by hand is impractical — it means looking up hundreds of thousands of positions one at a time. Software automates those lookups. BioDecode does this on your own machine: it reads the genome.txt, compares supported variant records with a local copy of ClinVar, and shows you only the entries that line up — no upload, no account. If that's the workflow you want, you can download BioDecode and run it offline.

However you do the matching, two cautions are not optional.

The two things that trip people up

Absence is not reassurance. The array only tests positions it was designed for. If a variant isn't in your file, that says nothing about whether you carry it — the chip simply may not look there. "Nothing found" is not a clean bill of health.

A match is not a diagnosis. Consumer raw data is uncurated; 23andMe states it is "suitable only for research, educational, and informational use." A 2018 study examined 49 patient samples referred for confirmation of consumer raw-data findings. In that selected sample, 40% of the evaluated variants were false positives. This is not an error rate for all consumer DNA data or all BioDecode results. A flag in your file is a lead to verify, not a verdict. Anything that looks medically significant should be confirmed in an accredited (CLIA) laboratory and discussed with a genetics professional.

Held to those limits, your raw data can be useful — a starting point for understanding your own genome on your own terms. For how the classifications themselves work, see how to find pathogenic variants in your raw DNA. If your data came from Ancestry instead, the AncestryDNA walkthrough covers the differences.

Analyze the file locally with BioDecode

Before purchasing, open the interactive example report. It contains demonstration data and shows the report layout without asking for your DNA. Use it to see whether the classifications, review status, and source links answer the questions you want to explore.

1. Install and activate. After purchasing, use the download links and license key sent by email. Follow the installation guide for your operating system.
2. Prepare the local database. Let the initial ClinVar download and database build finish before selecting your DNA file. Updating the database later also needs an internet connection.
3. Open your file. Drop the extracted text file into BioDecode. Keep the provider's headers and columns intact; there is no need to convert the file in a spreadsheet first.
4. Read the input summary. Check that the recognized file type and processing counts make sense. An error, skipped record, or unsupported format is not a negative finding.
5. Review annotations in context. Read classification, condition, genotype, and review status together. Follow source links when you need submission details. Those links open online resources; reading them is separate from local analysis.

BioDecode is made by DecodeLabs, which also publishes this guide. 23andMe does not endorse this product. The DNA privacy guide explains what to consider before sharing any raw file or exported report.

What to look for in the report

Suppose an illustrative row says “uncertain significance” and shows two ClinVar stars. That means the recorded classification is uncertain even though multiple submissions support it. It is not a prediction that you will develop a condition. Read what the ClinVar stars mean before using them to sort findings.

A report with few or no matches also needs context. The input may cover only selected positions, some records may not be usable, and ClinVar does not describe every possible variant. Keep the original file so you can distinguish the data you supplied from the annotations the software was able to report. If you need a medical answer, an educational report is not the endpoint.

Frequently asked questions

Is the 23andMe raw data file the same as having my genome sequenced?

No. It is genotyping-array data covering selected positions, not a sequence of your whole genome. It cannot report variants at positions the chip does not test.

What format is the file, and what opens it?

A tab-separated text file (genome*.txt) inside a zip. Any text editor can open it, but it is large and not meant to be read line by line — a tool that matches it against a variant database is far more useful.

Can I analyze it without uploading it anywhere?

Yes. Because it is just a local text file, desktop software can match it against a local copy of ClinVar entirely offline. BioDecode is built for exactly that.

A variant I care about isn't in my file — does that mean I don't have it?

No. The array only tests pre-selected positions. A missing marker can be untested, uncalled, filtered, or unsupported by the analysis. It does not establish that the variant is absent.

This article is educational and is not medical advice.

Prepared with AI assistance using the sources below. Published by DecodeLabs, the maker of BioDecode; not an independent clinical review.