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Misc LargestContentfulPaint updates #28658

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Merged
Elchi3 merged 3 commits into from
Dec 17, 2025
Merged

Misc LargestContentfulPaint updates #28658

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2ff0a29
Misc LargestContentfulPaint updates
tunetheweb Dec 13, 2025
bcbcafd
Update api/LargestContentfulPaint.json
tunetheweb Dec 17, 2025
a3dcbda
Update api/LargestContentfulPaint.json
tunetheweb Dec 17, 2025
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24 changes: 19 additions & 5 deletions api/LargestContentfulPaint.json
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Original file line number Diff line number Diff line change
Expand Up @@ -144,7 +144,14 @@
"spec_url": "https://w3c.github.io/paint-timing/#dom-painttimingmixin-painttime",
"support": {
"chrome": {
"version_added": false
"version_added": "134",
"flags": [
{
"type": "preference",
"name": "enable-experimental-web-platform-features",
"value_to_set": "enabled"
}
]
},
"chrome_android": "mirror",
"edge": "mirror",
Expand Down Expand Up @@ -175,19 +182,26 @@
"spec_url": "https://w3c.github.io/paint-timing/#dom-painttimingmixin-presentationtime",
"support": {
"chrome": {
"version_added": false
"version_added": "134",
"flags": [
{
"type": "preference",
"name": "enable-experimental-web-platform-features",
"value_to_set": "enabled"
}
]
},
"chrome_android": "mirror",
"edge": "mirror",
"firefox": {
"version_added": "140"
"version_added": false
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@Elchi3 Elchi3 Dec 17, 2025

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The collector detected support and it seems it is exposed. The null behavior seems to be per spec also? Maybe we should mark it as partial? (this is always weird for feature detection but oh well).

Suggested change
"version_added": false
"version_added": "140",
"partial_implementation": true,
"notes": "This property is exposed, but always returns `null`."

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@tunetheweb tunetheweb Dec 17, 2025

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It is effectively allowed per spec not to support this I agree, so it is an optional feature. But this is where it's even more important for MDN to document this IMHO.

Also I agree the fact it's there (but always null) could be interpreted as having "partial support". But to me, since it's always null, it's equivalent to "no support" rather than partial.

WDYT @canova from an Firefox side? And @smfr from a Safari size? Do you think it's fair to say you have not implemented presentationTime at this time for LCP? Note Interop and Baseline definitions do not include this key, and I'm keen to keep that this way, since these are optional, so you would still be marked as supporting LCP in those.

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@tunetheweb tunetheweb Dec 17, 2025 •
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Actually, let's go with partial support for now, to unblock this, since there are other updates in this PR I'd like to have sooner rather than later and partial is certainly better than the current reading of them having full support. But curious to hear @canova and @smfr's opinion and can follow up with another PR if necessary.

},
"firefox_android": "mirror",
"oculus": "mirror",
"opera": "mirror",
"opera_android": "mirror",
"safari": {
"version_added": "26.2"
"version_added": false
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@Elchi3 Elchi3 Dec 17, 2025

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Same here?

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@tunetheweb tunetheweb Dec 17, 2025

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Suggested change
"version_added": false
"version_added": "26.2",
"partial_implementation": true,
"notes": "This property is exposed, but always returns `null`."

},
"safari_ios": "mirror",
"samsunginternet_android": "mirror",
Expand Down Expand Up @@ -256,7 +270,7 @@
"opera": "mirror",
"opera_android": "mirror",
"safari": {
"version_added": false
"version_added": "26.2"
},
"safari_ios": "mirror",
"samsunginternet_android": "mirror",
Expand Down