Open Bug 1783718 Opened 6 months ago Updated 3 months ago

nglayout.initialpaint.delay Pref Does Not Affect Load Time of Some Sites


(Core :: Layout, defect)

Firefox 102



Tracking Status
firefox-esr91 --- unaffected
firefox-esr102 --- affected
firefox104 --- affected
firefox105 --- affected
firefox106 --- affected


(Reporter: jgt1970, Unassigned)


User Agent: Mozilla/5.0 (Windows NT 6.2; Win64; x64; rv:102.0) Gecko/20100101 Firefox/102.0

Steps to reproduce:

?User Agent String: Mozilla/5.0 (Windows NT 6.2; Win64; x64; rv:102.0) Gecko/20100101 Firefox/102.0

Set pref in about:config to 4000 ms. What I want is for most of the page to download first, and then load on screen in one fell swoop. This worked universally in Firefox ESR 91

Actual results:

On some sites, the setting is respected and works, but on other sites, the page starts rendering immediately, before it has completely downloaded.

I have tried defeating lazy load for images in about:config. No visible change though. I find when I load the top level page of a site, the browser waits to render the page as desired. Any other links on the page though load immediately. even when it's cached, there's a "flash" and the page loads. Before on ESR 91, the screen would switch seamlessly. is the best example. When you click on one of the grocery store icons on the right, the current flyers images start displaying right away while they are downloading. If I have the nnglayout.initialpaint.delay set to 4000, I shouldn't see anything for two seconds. And upon cached readings, I shouldn't see a blink and a quick display. I should see the page show up as quickly as possible, without blinking.

Also try The first page may load as desired, but go to the forum sub topics. They blink and start painting right away.

Expected results:

Now for contrast, here's a site that renders EXACTLY the way I want it to. On first load, the page, and all of the links load only when they are fully downloaded (as long as it's within four seconds), and upon revisiting a cached paged, it loads almost immediately, and with no "blink" or "flash". The first page doesn't clear before the next one loads. The pages just seamlessly switch.

I know, they're older sites, but just to show what my objective is a bit more clearly.

I've managed to reproduce this issue on the latest versions Nightly 106.0a1 and Firefox 104.0.1 on Windows 10 x64.
If this is not the correct component, please feel free to change it to a more appropriate one.

Severity: -- → S3
Has STR: --- → yes
Component: Untriaged → Preferences
Ever confirmed: true
Component: Preferences → Layout
Product: Firefox → Core
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