Intent to Prototype: Last Baseline Item Alignment

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Ian Kilpatrick

Sep 14, 2022, 2:11:12 PM9/14/22
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This feature allows developers to align items within either flex or grid layout by their last baseline, instead of their first. This is done via the following properties: align-items: last baseline; /* flex/grid container */ justify-items: last baseline; /* grid container */ align-self: last baseline; /* flex/grid item */ justify-self: last baseline; /* grid item */

Blink component



Currently in Blink we only support aligning grid/flex-items via. their first baseline. This feature allows web developers to align these items by their last baseline.

We previously supported *parsing* of these values, however disabled due to lack of layout support. See:

This intent does not cover the "align-content: last baseline" feature.

Initial public proposal

TAG review

TAG review status

Not applicable


Interoperability and Compatibility

Gecko: Shipping (

WebKit: Supports parsing of the property value - but doesn't currently support these in layout.

Web developers: No signals

Other signals:

WebView application risks

Does this intent deprecate or change behavior of existing APIs, such that it has potentially high risk for Android WebView-based applications?



This will show up as a valid value for these properties. A potential devtools feature would be to display where these baselines appear for each fragment.

Is this feature fully tested by web-platform-tests?

No. There are some WPT tests however they are incomplete (e.g. lack detailed testing). We'll add additional tests in the css-grid/css-flexbox directories as we implement.
There are multiple outstanding spec issues which we'll work through while implementing this feature. E.g.

Flag name

Likely --enable-blink-features=CSSLastBaseline will be available under --experimental-web-platform-features

Requires code in //chrome?


Tracking bug

Estimated milestones

Likely M108

Link to entry on the Chrome Platform Status

This intent message was generated by Chrome Platform Status.
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