Intent to Ship: CSS letter-spacing and word-spacing: percentage values

[Minseong Kim]

Contact emails

jja0...@gmail.com

Specification

https://www.w3.org/TR/css-text-4/#propdef-letter-spacing

https://www.w3.org/TR/css-text-4/#propdef-word-spacing

Summary

Enables percentage values for the letter-spacing and word-spacing CSS property, as defined in the CSS Text Module Level 4 spec. Percentage values are calculated relative to the advance measure of the space character (U+0020). This gives developers more robust and flexible control over typography, particularly in responsive designs where text spacing needs to adapt to different viewports and font sizes.

Blink component

Blink>Layout>Inline

Web Feature ID

letter-spacing

Search tags

letter-spacing, word-spacing

Risks

Interoperability and Compatibility

Risks are low. This is a support for new value of CSS properties. So sites not using properties won't be affected. Firefox and Safari has supported this feature for years.

Gecko: Shipped/Shipping Firefox is failing so many letter-spacing tests: https://wpt.fyi/results/css/css-text/letter-spacing?label=experimental&label=master&aligned. But those are related the line ending or boundary handling of letter-spacing, not the percentage values. Related discussion: https://github.com/w3c/csswg-drafts/issues/1518

WebKit: Shipped/Shipping (https://github.com/WebKit/WebKit/pull/18771)

Web developers: No signals (https://issues.chromium.org/issues/327740939) The issue has 3 votes.

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?

No information provided

Debuggability

No information provided

Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, ChromeOS, Android, and Android WebView)?

Yes

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

Yes
- "letter-spacing-percentage-001.html" file in https://wpt.fyi/results/css/css-text/letter-spacing - "word-spacing-percentage-001.html" file in https://wpt.fyi/results/css/css-text/word-spacing

Tracking bug

https://issues.chromium.org/issues/327740939

Estimated milestones

Shipping on desktop	145
Shipping on Android	145
Shipping on WebView	145
Shipping on iOS	145

Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/5074916059381760

This intent message was generated by Chrome Platform Status.

[Mike Taylor]

LGTM1

(aside, I see there are a few more relevant tests at https://github.com/web-platform-tests/wpt/commit/ffae172a1c2e44bddf71ca9430bc2aa519fbff6e)

Tracking bug

https://issues.chromium.org/issues/327740939

Estimated milestones

Shipping on desktop	145
Shipping on Android	145
Shipping on WebView	145
Shipping on iOS	145

Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/5074916059381760

This intent message was generated by Chrome Platform Status.

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[TAMURA, Kent]

It seems the chromestatus entry has an incorrect feature type, and API owners can't approve it.

Minseong, would you re-create an entry with "Chromium catches up" feature type please?

To view this discussion visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/384b8855-9a42-4504-8c61-221cccc49d9f%40chromium.org.

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TAMURA Kent
Software Engineer, Google

[Mike Taylor]

I wonder if Jason Robbins (cc'd) could convert this on the backend, so Minseong doesn't have to request new reviews, etc.

[Daniel Bratell]

LGTM2 - (I found a newly created entry in chromestatus that seemed to be the right one but let me know if it ends up messy)

/Daniel

To view this discussion visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAGH7WqFw98CuNe%2BMqOLfwnVZu65sTS9ghDGRCv_57_7-ZqLW%3DA%40mail.gmail.com.

[Mike Taylor]

Thank you - I've transferred the approvals from the old entry to the new one.

On 11/5/25 9:07 a.m., Minseong Kim wrote:

Oh, I've created a new chromestatus entry and sent an Intent to Ship mail. He doesn't need to convert this on the backend. Thanks for your help!
https://chromestatus.com/feature/5106867491700736

2025년 11월 5일 (수) 오후 10:51, Mike Taylor <mike...@chromium.org>님이 작성:

[Yoav Weiss (@Shopify)]

LGTM3

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[Minseong Kim]

Oh, I've created a new chromestatus entry and sent an Intent to Ship mail. He doesn't need to convert this on the backend. Thanks for your help!
https://chromestatus.com/feature/5106867491700736

2025년 11월 5일 (수) 오후 10:51, Mike Taylor <mike...@chromium.org>님이 작성:

I wonder if Jason Robbins (cc'd) could convert this on the backend, so Minseong doesn't have to request new reviews, etc.

[Minseong Kim]

Contact emails

jja0...@gmail.com

Specification

https://www.w3.org/TR/css-text-4/#propdef-letter-spacing
https://www.w3.org/TR/css-text-4/#propdef-word-spacing

Summary

Enables percentage values for the letter-spacing and word-spacing CSS property, as defined in the CSS Text Module Level 4 spec. Percentage values are calculated relative to the advance measure of the space character (U+0020). This gives developers more robust and flexible control over typography, particularly in responsive designs where text spacing needs to adapt to different viewports and font sizes.

Blink component

Blink>Layout>Inline

Web Feature ID

letter-spacing

Motivation

The 'letter-spacing' and 'word-spacing' properties currently only accept fixed length values (e.g. px, em), which are inflexible in responsive designs. When font sizes or container dimensions change, this fixed spacing can become disproportionate, forcing developers to write complex media queries or use JavaScript to maintain readable text. Introducing percentage values allows spacing to be defined relative to font-intrinsic metrics. This enables both letter and word spacing to scale proportionally with the font, simplifying the creation of robust and visually consistent typography across all devices without extra code.

Initial public proposal

No information provided

Search tags

letter-spacing, word-spacing

TAG review

No information provided

TAG review status

Not applicable

Risks

Interoperability and Compatibility

Risks are low. This is a support for new value of CSS properties. So sites not using properties won't be affected. Firefox and Safari has supported this feature for years.

Gecko: Shipped/Shipping Firefox is failing so many letter-spacing tests: https://wpt.fyi/results/css/css-text/letter-spacing?label=experimental&label=master&aligned. But those are related the line ending or boundary handling of letter-spacing, not the percentage values. Related discussion: https://github.com/w3c/csswg-drafts/issues/1518

WebKit: Shipped/Shipping (https://github.com/WebKit/WebKit/pull/18771)

Web developers: No signals (https://issues.chromium.org/issues/327740939) The issue has 3 votes.

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?

No

Debuggability

No information provided

Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, ChromeOS, Android, and Android WebView)?

Yes

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

Yes
- "letter-spacing-percentage-001.html" file in https://wpt.fyi/results/css/css-text/letter-spacing
- "word-spacing-percentage-001.html" file in https://wpt.fyi/results/css/css-text/word-spacing

- "letter-spacing-*.html" files in https://wpt.fyi/results/css/css-text/parsing
- "word-spacing-*.html" files in https://wpt.fyi/results/css/css-text/parsing

Flag name on about://flags

enable-experimental-web-platform-features

Finch feature name

CSSLetterAndWordSpacingPercentage

Rollout plan

Will ship enabled for all users

Requires code in //chrome?

False

Tracking bug

https://issues.chromium.org/issues/327740939

Estimated milestones

Shipping on desktop	145
Shipping on Android	145
Shipping on WebView	145
Shipping on iOS	145

Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/5106867491700736?gate=6484265969778688