Re: [csswg-drafts] [css-borders] Add a 'hairline' border-width value (#3720)

> This makes me wonder why hairline is needed at all if you can do `--hairline: border-round(0.01px);`

Using 0.01px is kind of fragile, though. For example, a `0.008px` border doesn't render in Firefox, because before pixel snapping, it uses a unit precision of 1px/60, and 0.008 is closer to 0 than to 1/60. But Chrome seems to store it as a float, because even a `0.00000000000000000000000001px` border is visible.

Note the 1px/60 precision is UA-specific, e.g. Blink uses 1px/64, and IE used 1px/100. So it's plausible that some browser would use a unit precision of 1px/30, and store the value using units (rounding to closest). Then `border-round(0.01px)` would be 0.

Having a hairline you wouldn't need to worry about this kind of problems.

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Received on Friday, 16 January 2026 21:50:49 UTC