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• As far as I'm aware we generate a thumbnail for every version. When you make changes the update gets queued. The delay depends on the size of the queue. • Yes, for the specific version. • We pick the first svg, img, canvas or table above a certain size. In general we encourage authors to set a custom thumbnail. There are a lot of factors that can cause thumbnails to not generate properly, e.g. when external dependencies in your notebook load delayed, or the first image or plot requires a lot of upfront processing.

Thanks for the info. Just to explain my questions: We are thinking of using the thumbnails in our website in an overview that can be filtered by a tag system. Since there will be a lot of charts, a manual solution is not very practical in our case. But we might have to build our own thumbnail generator, since we would also like to regenerate the thumbnail if the unterlying data changes (from an api).

Are you planning to embed the notebooks into your site, or do you want to point the links to Observable? And do you intend to publish your notebooks as unlisted?

We intend to embed the notebooks and we don't have a particular policy concerning listing or unlisting the notebooks. I think we don't care if they are listed.

Unfortunately we don't have any official API to fetch or to update thumbnails. Your idea of using your own thumbnail generator seems reasonable. The alternative would be to scrape the information from our internal API (which we neither endorse nor support 🙂).

<https://api.observablehq.com/document/ce966ce69353f815/head>

{
    "creator": {
...
    },
    "fork_of": true,
    "id": "ce966ce69353f815",
    "owner": {
...
    },
    "slug": "zahlen-und-fakten-in-bildung/1234",
    "thumbnail": "a0a5f7c6e517ecb12b411448a92f599259aa911bf559be95afbc74ca6f074282",
    "title": "Zahlen und Fakten in der Bildung (Grafik 1 bis 4), Überblick Primar- und Sekundarschule, Berufs- und Mittelschule",
    "update_time": "2023-04-19T11:17:09.053Z",
    "version": 3691
}

Thanks for looking into my problems. I think I now have the necessary information to continue with with our tasks.

A few clarifications to what I wrote earlier:

As far as I'm aware we generate a thumbnail for every version.

We make an effort to generate a thumbnail for every current version, but will debounce generation. So not every version will have a thumbnail.

Yes, for the specific version.

While we only track the latest thumbnail, we currently don't delete old thumbnails, and there are no plans to change that.