Share via public URLs

We want to allow researchers the maximum amount of control over where their data lives and who controls it. To facilitate this, we promote a couple of easy-to-use methods to facilitating this - Nextstrain Groups, where the data are stored on, and Nextstrain Community, where the data lives within your own GitHub repos. This page describes a third way:

Datasets or narratives which are accessible via a public URL can be accessed through a URL

  • Given an Auspice v2 dataset JSON available at https://A.B.C.json, the dataset may be accessed via

  • Given a narrative markdown file publicly available at, the dataset may be accessed via


  1. Single dataset The Nextstrain zika dataset is accessible at (click that link to see the actual JSON data) and can therefore be viewed within at

  2. Narratives There is an introductory narrative stored in our GitHub repo and therefore accessible via the URL (click there to read the actual markdown file). You can see this rendered in Nextstrain at:

  3. Dual trees Displaying two trees side-by-side is possible using the same syntax as with other dataset sources, e.g.


HTTPS only The HTTPS protocol is mandated, but “https://” must be left out of the datset URL when it’s written as part of the Nextstrain URL. Formally, only the hier-part of the URL is used – we mandate the scheme to be HTTPS and ignore any queries (or fragments).

Colons not allowed The colon (:) is reserved as the separator for dual tree displays so they are not allowed in the dataset URL. Using URLs with colons will result in 404 errors.

Suffixes not required The above examples have assumed that the URL for the dataset JSON ends with .json, as is often the case, but this isn’t required! For instance, you could have a server which generates a JSON at https://my-server/makeMeADataset and access this via

Sidecar files (such as tip-frequency JSONs) are fetched similarly to other sources – e.g. if the dataset is at https://A/B.json then a subsequent request to https://A/B_tip-frequencies.json will be made. If the fetch URL doesn’t end in .json then the GET request would be to https://A/B_tip-frequencies.

Authentication is not currently supported. Please see Nextstrain Groups for this!

How do I manage the data storage?

That’s completely up to you - all that we require for this to work is that it’s publicly accessible via a URL over HTTPS. It could be a static asset (e.g. AWS S3) or a server which responds dynamically. We recommend the the data is transmitted using compression to improve loading times for the client.

P.S. If you build something interesting here, for instance a server which generates the JSON on-the-fly, we’d love to hear from you!.