Re: [community-group] Dimension type expanded unit types (#245)

@brettdorrans That won't work in practice because the CSS unit list isn't something that works cross platform. Not all CSS units can be "transpiled" to something that makes sense in iOS, Android, ...

While I agree in principle that more units should be adopted I don't think that allowing anything is a good design.

Please re-read all my comments in this thread :)

The issue at hand is not about allowing or disallowing specific units or even about keeping the list of adopted units small.

It is about keeping the list defined locally or instead allowing any units.

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> For $type: "dimension" tokens, define $value as a dimension: a number followed immediately by a unit string. The unit MAY be any valid CSS unit (as defined by the CSS Values and Units Module [w3.org](https://www.w3.org/TR/css-values-4/#:~:text=6,pc%20%2C%20px%20units)) or any other string. If an unfamiliar unit is used, tools MAY issue a warning but MUST NOT reject the file.

That is separate from this issue.

See:
- https://github.com/design-tokens/community-group/pull/244
- https://github.com/design-tokens/community-group/issues/121

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> Remove or make optional any vendor field. Vendors can still use prefixes if they wish, but nothing in the carrier format should require it.

I don't really understand this point.
What is the benefit to allowing any tool vendor to allowing their own units, thereby poisoning the well for everyone. Please remember [smooshgate](https://developer.chrome.com/blog/smooshgate)

This a sidetrack. The `vendor` field proposal is an extra idea. It defines a possible way to combine the restrictions of a defined unit list with wanting to ship early features in tools.

There will always be tention between:
- what is supported in platforms (e.g. container relative units from CSS vs. iOS/Android)
- specification
- what has shipped in tools
- which features users want
- which features users have adopted

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> Keep the specification focused on interoperability. Do not replicate CSS's unit list. Instead, reference the CSS spec for definitions of units.

Interop between multiple platforms (iOS, Android, Web, ...) is also an important factor for this specification.

Allowing a large number of CSS units that don't mean anything in other platforms isn't really good interoperability.

Each unit needs to be defined such that tool makers know how to transpose values.

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Received on Monday, 15 September 2025 06:52:40 UTC