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List: webkit-dev
Subject: Re: [webkit-dev] WebKit position on Paint Timing / (first paint, first contentful paint)
From: Noam Rosenthal <noam () webkit ! org>
Date: 2020-02-26 19:38:11
Message-ID: CAGttnEXEo1=3kWBvj3GYQ6zRqgj-Bcx8uPuo-3_CbQvbvZaD1w () mail ! gmail ! com
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On Wed, Feb 26, 2020 at 9:29 PM Maciej Stachowiak <mjs@apple.com> wrote:
> I also suggest to start with "first-paint" as it's perhaps a bit less
> "internal" than FCP, and can provide a performance-regression metric with a
> lesser degree of risk regarding exposing internals / privacy.
>
>
> First paint that's not first meaningful/contentful paint is not a very
> good performance metric IMO. Who cares that a paint happened if it doesn't
> have any image or text content?
>
I think it's meaningful as a general regression metric, albeit less useful
than FCP. Web developers are scrambling for any RUM information they can
use...
> I also don't think this exposes less. The privacy risk here is exposing
> timing data that might be usable for fingerprinting.
>
Yes, I think that privacy-relevant timing information is already available
through resource timing (window.performance.getEntries("resource")). But
we'll see what the privacy experts come up with.
> What was deprecated was "first meaningful paint" (FMP). FCP was not
> deprecated and has been in wide use for some time.
>
> What's the difference between First Meaningful and First Contentful?
>
FMP had the notion of "primary" content; e.g. it was ignoring
navbars/headers, and trying to figure out when the main content of the site
has been rendered. As noted, FMP is deprecated. FCP is a lot more
transparent in what it measures.
We will discuss with Apple's privacy experts what they think of the privacy
> risk. I'm just giving you a rain check for results of this discussion.
>
Got it, Looking forward :)
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<div dir="ltr"><div dir="ltr"><br></div><br><div class="gmail_quote"><div dir="ltr" \
class="gmail_attr">On Wed, Feb 26, 2020 at 9:29 PM Maciej Stachowiak <<a \
href="mailto:mjs@apple.com">mjs@apple.com</a>> wrote:<br></div><blockquote \
class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid \
rgb(204,204,204);padding-left:1ex"><div style="overflow-wrap: \
break-word;"><div><blockquote type="cite"><div><div dir="ltr"><div \
class="gmail_quote"><div>I also suggest to start with "first-paint" as \
it's perhaps a bit less "internal" than FCP, and can provide a \
performance-regression metric with a lesser degree of risk regarding exposing \
internals / privacy.</div></div></div></div></blockquote><div><br></div><div>First \
paint that's not first meaningful/contentful paint is not a very good performance \
metric IMO. Who cares that a paint happened if it doesn't have any image or text \
content?</div></div></div></blockquote><div>I think it's meaningful as a general \
regression metric, albeit less useful than FCP. Web developers are scrambling for any \
RUM information they can use... <br><br></div><blockquote class="gmail_quote" \
style="margin:0px 0px 0px 0.8ex;border-left:1px solid \
rgb(204,204,204);padding-left:1ex"><div style="overflow-wrap: \
break-word;"><div><div><br></div><div>I also don't think this exposes less. The \
privacy risk here is exposing timing data that might be usable for \
fingerprinting.</div></div></div></blockquote><div>Yes, I think that privacy-relevant \
timing information is already available through resource timing \
(window.performance.getEntries("resource")). But we'll see what the \
privacy experts come up with. </div><div> </div><blockquote class="gmail_quote" \
style="margin:0px 0px 0px 0.8ex;border-left:1px solid \
rgb(204,204,204);padding-left:1ex"><div style="overflow-wrap: \
break-word;"><blockquote type="cite"><div dir="ltr"><div \
class="gmail_quote"><div>What was deprecated was "first meaningful paint" \
(FMP). FCP was not deprecated and has been in wide use for some \
time.</div></div></div></blockquote><div>What's the difference between First \
Meaningful and First Contentful?</div></div></blockquote><div>FMP had the notion of \
"primary" content; e.g. it was ignoring navbars/headers, and trying to \
figure out when the main content of the site has been rendered. As noted, FMP is \
deprecated. FCP is a lot more transparent in what it \
measures.<br><br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px \
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div \
style="overflow-wrap: break-word;"><div>We will discuss with Apple's privacy experts \
what they think of the privacy risk. I'm just giving you a rain check for results of \
this discussion.</div></div></blockquote><div>Got it, Looking forward :)<br> \
</div></div></div>
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