Re: [csswg-drafts] [css-backgrounds] Always serialize 'background-size' and `mask-size` as two values (#7802)

The list of pages (random 1% subset), ordered by rank, using single-value length or percentage for -webkit-background-size:

Row | page | rank
-- | -- | --
1 | `https://evolve.edufocus.co.uk/` | 50000
2 | `https://emcitv.com/` | 50000
3 | `https://e.walla.co.il/` | 50000
4 | `https://ec.jal.co.jp/` | 50000
5 | `https://elmir.ua/` | 50000
6 | `https://eloto.tg/` | 50000
7 | `https://earnkaro.com/` | 50000
8 | `https://eju.tv/` | 50000
9 | `https://elibro.net/` | 50000
10 | `https://en.hdsex.fun/` | 50000
11 | `https://erovns.com/` | 50000
12 | `https://en.paradisehill.cc/` | 50000
13 | `https://loteriadebogota.com/` | 100000
14 | `https://www.ventanillamovilidad.com.co/puntos-de-atencion` | 100000
15 | `https://logo-editing.fandom.com/` | 100000
16 | `https://learngerman.dw.com/` | 100000
17 | `https://lovein.asia/` | 100000
18 | `https://www.u-tokyo.ac.jp/ja/about/president/plog_2025_0506.html` | 100000
19 | `https://lk.samgtu.ru/` | 100000
20 | `https://www.ull.es/portal/convocatorias/categorias/investigacion/` | 100000

Checking a few, they seem to use autoprefixer and just use the same value for prefixed as unprefixed, and letting the unprefixed variant win.

Gecko has the same parsing behavior for prefixed as unprefixed ([demo](https://software.hixie.ch/utilities/js/live-dom-viewer/saved/13967)). From a quick search I found no bugs about -webkit-background-size. Maybe Chromium and WebKit can change -webkit-background-size into a proper alias of background-size?

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Received on Tuesday, 5 August 2025 09:33:14 UTC