Key Points

The datasette.io site’s “news” section is generated from a GitHub-stored `news.yaml` file, using YAML entries with `date` and Markdown `body` content.
The article explains the YAML format is difficult to edit reliably, so a custom “news preview” UI was built to reduce friction and catch formatting issues before publishing.
The preview tool was created with Claude (including repo cloning and artifact generation) to both render the YAML and highlight YAML/Markdown validation errors, such as an invalid `date` format.
The walkthrough emphasizes a workflow improvement: paste-edit YAML and immediately see the rendered homepage output plus error indicators.
A visual example shows side-by-side editing and preview, with a validation error badge to help ensure correctness of news entries.

Simon Willison’s Weblog

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16th April 2026

Tool datasette.io news preview

The datasette.io website has a news section built from this news.yaml file in the underlying GitHub repository. The YAML format looks like this:

- date: 2026-04-15
  body: |-
    [Datasette 1.0a27](https://docs.datasette.io/en/latest/changelog.html#a27-2026-04-15) changes how CSRF protection works in a way that simplifies form and API integration, and introduces a new `RenameTableEvent` for when a table is renamed by a SQL query.
- date: 2026-03-18
  body: |-
    ...

This format is a little hard to edit, so I finally had Claude build a custom preview UI to make checking for errors have slightly less friction.

I built it using standard claude.ai and Claude Artifacts, taking advantage of Claude's ability to clone GitHub repos and look at their content as part of a regular chat:

Clone https://github.com/simonw/datasette.io and look at the news.yaml file and how it is rendered on the homepage. Build an artifact I can paste that YAML into which previews what it will look like, and highlights any markdown errors or YAML errors