A Free Promethease Alternative
Twofold explains your raw DNA data with SNPedia, the same source Promethease uses. It's free, open source and runs entirely in your browser, so your file never leaves your device.
Built on the same SNPedia entries
Twofold matches your genotypes against SNPedia, the community wiki of SNPs and what each genotype means. It reads a snapshot taken October 16, 2026, so a few entries may differ from other SNPedia-based reports.
- 104,732 genotypes
- 111,734 SNPs
- 283 genosets
Your file never leaves your browser
Your raw data is read by a Web Worker on your own device, and the site has nowhere to upload it. Watch your browser's Network panel while a report builds: every request fetches part of the app or its SNPedia data from Twofold's own site, and your file is never one of them.
- Works offline
- No account
- How to check it yourself
Free, and open to inspect
There is no fee, no account and no subscription. The code that reads your file and builds your report is public, so you can see exactly how your data is handled instead of taking it on trust.
Inside the report
Ranked findings
Every match between your file and SNPedia, sorted by magnitude, with filters for repute, chromosome, topic and rare variants.
Topics
Findings grouped by gene, condition and medicine, so you can follow one subject through your data.
Genosets
Combinations of genotypes that SNPedia reads together, checked against your whole file.
Strand handling
Letters from 23andMe and AncestryDNA files are matched to SNPedia's orientation, including SNPs SNPedia lists on the minus strand.
A public SNP database
Every notable SNP has its own page in Explore, so you can read about a variant before or after you open your file.
Questions
Does Twofold use the same data as Promethease?
Both Twofold and Promethease are built on SNPedia, the community-edited wiki that describes SNPs and what each genotype means. Twofold reads a snapshot of SNPedia taken October 16, 2026, covering 104,732 genotypes across 111,734 SNPs, plus 283 genosets. SNPedia keeps changing, so a few entries may differ from what other SNPedia-based reports show.
Can I use the raw data file I used with Promethease?
Yes. Twofold reads the raw data file you download from your testing service, the same kind of file Promethease uses. If you no longer have it, you can download it again from 23andMe, AncestryDNA, MyHeritage or your other provider.
Is Twofold really free?
Yes. Twofold costs nothing to use, with no account, no subscription and no limit on how many files you open. It is an independent, open source project, and you can support it with a donation if you find it useful.
Is my DNA file uploaded anywhere?
No. Twofold reads your file in a Web Worker inside your browser and builds the report on your own device. The site has no upload endpoint, and the only thing your browser fetches from it is the app and the same SNPedia reference data every visitor gets. After your first complete visit it works offline. The privacy page explains how to check this yourself in your browser.
Which raw data files work with Twofold?
Twofold reads raw data from 23andMe, AncestryDNA, MyHeritage, FamilyTreeDNA and Living DNA, plus VCF files from whole genome sequencing. You can open the file exactly as you downloaded it, including ZIP and GZ archives, without unzipping it first.
Can I save or export my report?
Reports stay in memory by default and are cleared when you close the tab. You can save an encrypted copy in your browser, protected by a passphrase, export your findings as CSV or JSON, or print the report and save it as a PDF. Your raw file itself is never saved.
Is a Twofold report a medical diagnosis?
No. SNPedia is community-edited, so its entries can be incomplete, out of date or wrong, and its magnitude is a rating of interest rather than a risk score. Consumer DNA tests can also misreport very rare variants. Talk to a doctor or genetic counselor, and confirm important findings with a clinical test before acting on them.