Baseline's April updates: new web platform features and expanded tooling

April brought a steady stream of Baseline news, from newly available web platform features to a wave of tooling integrations that make it easier to code against Baseline targets. Here's a summary of what changed.

Newly available and Widely available features

Two features moved into Baseline Newly available status this month:

  • Float16Array
  • Single color stop gradients

Two more became Baseline Widely available:

  • Animation support for the grid-template-columns and grid-template-rows CSS properties
  • The CSS ic unit

Baseline support arrives in Visual Studio Code Insiders

Work has been underway to fold Baseline information into Visual Studio Code. In the Insiders build, hovering over CSS rules and HTML elements now shows tooltips that indicate whether a feature has reached Baseline status. That means you can get immediate feedback on whether the HTML and CSS you're writing is broadly supported, without leaving the editor.

The change is currently limited to the Insiders build but should reach stable in the near future. Because the implementation builds on VS Code's architecture, other editors based on it should also pick up the capability. Meanwhile, support has already landed in Zed, although there is a known issue affecting how the Baseline icon displays there.

Stylelint gains a Baseline plugin

ESLint recently added a use-baseline rule for flagging CSS features based on their Baseline status. Stylelint users now have an equivalent option with new package stylelint-plugin-use-baseline. The rule works much the same way but is suited to projects that prefer Stylelint for CSS linting. As with the ESLint rule, a GitHub demo repo under baseline-demos/tooling/stylelint shows the plugin in a working Stylelint pipeline.

ESLint's use-baseline rule gets more control

The ESLint CSS linting project continued to mature, with several updates to its use-baseline rule:

  • Configuration can now target a specific Baseline year rather than only "newly" or "widely" values, giving finer control over which features trigger warnings or errors.
  • Selectors can now be linted for Baseline support. Previously, only other parts of stylesheets were covered, despite selectors being discrete features that can become Baseline themselves.
  • Support for additional CSS functions has been expanded, including color-mix and conic-gradient, among others.
  • The rule now warns by default instead of erroring, so builds won't fail unless you explicitly opt into error-level behavior.

New package bridges Baseline and Browserslist

Many build pipelines rely on a Browserslist configuration to drive output decisions in PostCSS, Babel, and related tools. The newly released browserslist-config-baseline package translates a Baseline target—such as Widely available, Newly available, or a specific year like Baseline 2024—into a valid Browserslist query.

That translation opens up several workflow options. You can tailor generated CSS and JavaScript to your chosen Baseline target, including controlling polyfill behavior through tools like core-js and Babel. The net effect can be less shipped code and better performance. For concrete examples, the project team has published Babel and PostCSS demos in the baseline-demos GitHub repository.

The package builds on the underlying baseline-browser-mapping package, which also saw new capabilities: a new nested object format for output when fetching all browsers, data on which browser versions support Newly available features, and automatically generated static versions of getAllVersions() that are easier to embed in analytics or data-matching systems.

More resources and demos

In a RUMvision webinar, Google's Tony Conway joined Erwin Hofman for an introduction to Baseline and a look at how Google teams are working together on the initiative. It offers a useful walkthrough of how Baseline fits together.

The baseline-demos repository also continues to grow its tooling section. Notable among the examples is a Baseline MCP server you can connect to AI coding agents, which can help make generated code more Baseline-aware. Expect new tooling demos to be added over time.