A web-based preview tool for datasette.io news entries that validates YAML format, checks markdown syntax, and provides real-time rendering of news entries. Built with Claude AI to reduce friction in editing the site's news.yaml file.
# Tool: datasette.io news preview
Source: https://simonwillison.net/2026/Apr/16/datasette-io-preview/
[datasette.io news preview](https://tools.simonwillison.net/datasette-io-preview) — Preview and validate datasette.io news entries in YAML format with real-time rendering and markdown linting. The editor loads the current news.yaml file from GitHub and provides immediate feedback on formatting errors, link validation, and markdown syntax issues while displaying a styled preview of how entries will appear on the live site. Use the error badge to track validation issues and fix them directly in the editor pane.
The [datasette.io](https://datasette.io/) website has a news section built from this [news.yaml](https://github.com/simonw/datasette.io/blob/main/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](https://claude.ai/share/c96129b9-bcb0-4eba-aee9-4a7ad236dfb7) to make checking for errors have slightly less friction.
I built it using standard [claude.ai](https://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`
Screenshot showing two side-by-side views of a datasette.io news preview tool. The left panel shows a dark-themed YAML editor with news entries containing date and body fields in Markdown format, with a red validation error at the bottom indicating the date field has an invalid format. The right panel shows the rendered preview output with formatted headings by date (April 2026, 18th March 2026), displaying 115 news entries with linked release names, inline code snippets, and changelog descriptions. A red badge with "1" appears on the left panel header indicating one validation error.
A markdown rendering tool that supports live preview, table and code block formatting, and special handling for SVG code blocks with inline preview and tabbed code view.
Datasette 1.0a34 introduces built-in tools for inserting, editing, and deleting rows directly in the Datasette interface, a feature long overdue and inspired by Datasette Agent.
Datasette 1.0a29 is released with new utility methods, UI improvements for empty tables, and bug fixes including a race condition resolved with help from Codex CLI.