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If you've just downloaded your 23andMe raw data, there's a zip file in your Downloads folder with a name that starts with "genome", and a page of search results full of sites that would like you to send it to them. Before you do, it helps to know what's actually in that file, what it's good for, and what changes once a copy of it leaves your computer.
Your file is a long list of letters, and you can read it yourself
Unzip the file and open it in a plain text editor. After a few lines of notes at the top, every row looks something like this:
rs1801133 1 11856378 AG
That row has four parts. The first is the marker's ID, an "rs number" from the NIH's dbSNP database, which is how researchers everywhere refer to the same spot in the genome. Then the chromosome it sits on (1), its position on that chromosome, and your genotype: two letters, because you carry two copies of most chromosomes, one from each parent, as 23andMe's guide to its genotypes puts it. AncestryDNA files split the genotype into two columns, but the idea is the same.
This particular row is a marker in MTHFR, a gene that helps your body use folate, and it's one of the markers the Methylation and Diet Report reads.
A file holds somewhere around 600,000 to 700,000 of these rows. A 2024 research preprint on genotype imputation, for example, describes 23andMe's current chip as reading 642,824 markers. Companies change their chips over time, so two files from the same company can hold different markers depending on the year you tested. We walk through what that means for one well-known gene in our guide to finding your APOE type in your raw file.
You'll also see a few rows where the genotype is "--" in a 23andMe file or "0 0" in an AncestryDNA file. These are no-calls, spots the lab left blank because it couldn't get a clear reading. A scattering of them is normal and doesn't mean anything went wrong.
Getting the file takes a few clicks, and sometimes a week
Every company keeps the download a few steps deep, and each one asks you to confirm it's really you.
23andMe. Click your profile name at the top right, choose Resources, then Browse Raw Genotyping Data, then Download. Confirm your date of birth, read the notes, tick the box and submit the request. 23andMe says the email telling you your file is ready usually takes about a week and can take up to thirty days, and you'll confirm your birthdate again before the download starts.
AncestryDNA. Go to DNA Settings and pick your test. Under Download or Delete, choose Download DNA data, tick the box and verify with your password or an emailed code. Ancestry's help page says the email can take up to 24 hours, and its link works only once and expires after a week. The file arrives as a zip named dna-data with the date.
MyHeritage. Open the DNA menu, go to Manage DNA kits, click the three dots beside your kit and choose Download, then the DNA data file. MyHeritage's instructions say the emailed link lasts 24 hours, only the kit's manager can download it, and it works on a computer or an Android device but not on an iPhone or iPad.
FamilyTreeDNA. Sign in and go to Results & Tools, then Autosomal DNA, then Download Raw Data. FamilyTreeDNA requires two-factor authentication before it will let you download, and its file comes as a GZ archive that the built-in Mac and Windows tools can't open. If you'd like to use a FamilyTreeDNA file with Noorns, email info@noorns.com first and we'll tell you whether it works.
The same steps for the three biggest services, kept up to date, are on our Get your DNA file page.
It's reliable for common variants, and that's where it's most useful
The best evidence on how accurate these files are comes from a study of nearly 50,000 UK Biobank participants published in The BMJ in 2021. The researchers compared chip results with full sequencing of the same people. For 108,574 common variants, the chips agreed with sequencing more than 99% of the time. For very rare variants, the kind carried by fewer than 1 in 100,000 people, only 16% of the chip results held up.
Both halves of that finding help you use your file well. It's very good at the common variants, which are the ones most nutrition research is built on. Take the MTHFR marker in the row above. In the 1000 Genomes reference data listed in NIH's dbSNP database, about one in four copies of it carry the A version, so it's anything but rare. That makes food and nutrient questions a natural fit for what the chip reads well.
Very rare disease variants are a different matter. If a tool flags one in your file, treat it as a reason to ask your doctor about a clinical test, not as a result. The study's authors concluded that chips shouldn't guide health decisions about rare variants without that kind of confirmation, and 23andMe itself says its raw data is for informational use, not medical or diagnostic use.
Once the file leaves your account, the copy is yours to look after
While your raw data sits inside your 23andMe or Ancestry account, the company that tested you is responsible for protecting it. Once you download it and send it somewhere else, that changes. The National Human Genome Research Institute explains that if you download your genetic information from one service and upload it to another, "the company that originally collected the data is no longer responsible for any breach of privacy that may occur."
The testing companies say the same about their own downloads. Ancestry warns that once you download your DNA data, "your downloaded copy is no longer under the protection of our security measures." MyHeritage asks you to accept responsibility for the copy before it will let you have it.
That's a reason to choose carefully where the file goes, not a reason to leave it unused. In 2023, attackers using passwords leaked in other breaches got into about 14,000 23andMe accounts, according to The Guardian, and the UK's data regulator later fined the company for not adding an extra check before raw data could be downloaded. After 23andMe filed for bankruptcy in March 2025, about 15% of its customers asked for their genetic data to be deleted.
A Noorns report doesn't add another copy to look after. It reads your file in your own browser, and your DNA file is never uploaded to us or stored by us, so the copy on your computer is still the only one.
Questions to ask any service before you give it your file
You can still put your file to good use. These questions help you choose where it goes. They come straight from the testing companies' own advice, plus one of ours, and they work on any service you're considering, Noorns included.
- Does it read the file in your browser, or send it to a server? If the file never leaves your computer, most of the questions below stop mattering. That's how Noorns works, so for a Noorns report you can skip the rest of this list.
- If it keeps a copy, can you delete it whenever you like? Ancestry suggests checking for this before you upload anywhere.
- Is there a privacy policy you can actually read, and, if your data could be used in research, an ethics board overseeing that? Also from Ancestry's list.
- Is your account protected with two-factor authentication? MyHeritage singles this out as the thing to check.
- What happens to your data if the company is sold or closes? The 23andMe sale is the reason to ask.
Most of what you want from your file can happen on your own computer
Start by keeping one master copy somewhere safe, such as an encrypted drive or a password-protected folder, and work from a duplicate. Our guide to DNA file privacy walks through a simple routine for this.
If you've read about a particular marker, you can look it up yourself. Search the file for its rs number in any text editor and read the two letters beside it. The APOE guide linked above shows the whole process with two real markers, no-calls included.
For a fuller picture, use a tool that reads the file in your browser rather than one that asks you to send it. Noorns works this way.
Where to start if you want to know what your genes mean for food
Most people looking for what their genes mean for nutrition start with the Methylation and Diet Report. It reads 61 genes across six areas, including MTHFR and folate, choline, riboflavin and histamine, and weighs them against the research behind each one. The report runs to more than 100 pages, and it's built around a short, ranked list of the foods, nutrients and habits to focus on and the ones to go easy on, with food first and supplements named in the exact form.
It's made in your own browser. You attach your file, keep the tab open for three to ten minutes, and save the PDF. Your DNA file is never uploaded or stored. Each purchase includes up to three report runs, so a lost PDF or an updated version doesn't cost you another report.
The report shows tendencies in your genes rather than a diagnosis, and it works best alongside lab work with a practitioner, who can measure what's happening in your body today. If you'd like to see what one looks like first, read an example report made from a sample DNA file.
Questions about your raw DNA file
Is it safe to upload my raw DNA file?
It depends on who receives the copy and what they do with it. Once the file leaves your testing company, the protection that came with your account no longer covers it. Run through the questions above, or use a tool that reads the file without it leaving your computer. Our post on whether it's safe to put your DNA into ChatGPT covers chatbots in particular.
Which raw DNA files work with Noorns?
Raw data files from 23andMe, Ancestry, MyHeritage and SelfDecode work today. Tested somewhere else? Email info@noorns.com and we'll tell you whether your file works.
Can my raw data diagnose a disease?
No. The testing companies say their raw data is for information, not diagnosis, and the chips are least reliable for exactly the rare variants a diagnosis would turn on. Where the file is reliable is the common variants, which is why it's useful for understanding tendencies, like how your genes handle certain nutrients.
What does "--" or "0 0" mean in my file?
It's a no-call: the lab couldn't read that marker with confidence, so it left it blank rather than guess. A small number of these is normal.
Does a DNA report replace my doctor?
No. A report shows tendencies in your genes and gives you food and nutrient priorities to explore. Your genes point you to where to look, and lab work with a practitioner measures what's happening in your body today, so the two work best together.
