About Twofold

Twofold compares a raw DNA file with a dated copy of SNPedia, entirely in your browser. It's a free, open source project by Brandon Saldan, first released as GeneCodex in 2023.

What the results mean

Many genetic associations are uncertain, population-specific or later revised. SNPedia's magnitude is a community rating of interest, not a risk score. Good and bad are community labels. A single genotype does not diagnose a condition or tell your whole story.

Consumer genotyping chips can produce false positive calls for very rare variants. Important findings should be confirmed through clinical testing before you act on them. See Weedon and colleagues, BMJ 2021.

Every notable SNP also has its own page in the SNP database, and if you have used Promethease before, here is how Twofold compares.

Credits and licenses

Genetic annotations come from SNPedia, a community wiki. SNPedia content and the derived reference dataset are shared under CC BY-NC-SA 3.0 US. Source entries can be read on SNPedia. The app's own source code is available under its repository license.

Twofold uses self-hosted Newsreader, Schibsted Grotesk and IBM Plex Mono fonts.

Source code

View Twofold on GitHub. The repository includes the file parser, the SNPedia data builder and the tests.