Growing FID on mobile devices

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Mar 21, 2021, 6:11:55 AM3/21/21
to web-vitals-feedback

Hi, unfortunately I need some help again. My website is suffering from a growing FID since about 3 weeks and I don't find a way to stop or even reduce it. The FID is now about 203 ms and no hope that it stops here.

I have removed all render blocking CSS.
I have removed all render blocking JS, except JQuery because it is needed by some applications. Unfortunaley it leads somestimes to the info reduce main thread work on mobile devices. (Growing FID was already a problem before that action!)
I have minified CSS and JS.
I have deactivated Social Media Sharing for a splitt test. No difference...

There is no problem with Time to Interactive or Total Blocking Time. Both are green.

What is causing the FID? Maybe someone can help me.

Greetings Kathrin

Nicolás Peña Moreno

Mar 22, 2021, 1:05:13 PM3/22/21
to Topfgartenwelt, web-vitals-feedback
I'm not really able to reproduce locally, so it's not clear to me what the problem is. Trying to get local repro would be one thing to try. If possible get more info from cases that are seeing high FID values. One thing that could cause high FID without having lots of JS is tap delay zoom (see article). We're working on making this easier.

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Mar 23, 2021, 6:16:51 AM3/23/21
to web-vitals-feedback
My site is flagged for a problem that can't be reproduced? My theme-developer also can't reproduce the problem too, but I can see the high FID with the Chrome Extensions for Core Web Vitals when clicking into an input field??? And most of my users see it too? Now the FID started also to grow on Desktop and there is no help?

Aleksey Kulikov

Mar 23, 2021, 6:26:44 AM3/23/21
to web-vitals-feedback
Hey Kathrin, 
I checked your website, and this may be the cookies banner. Visitors click it to accept cookies (First Input), and it produces substantial delays that are easy to catch in Dev Tools. 
It appears only for EU visitors. In February, your metrics were good: 
Screen Shot 2021-03-23 at 11.19.44.png


Mar 24, 2021, 4:40:15 PM3/24/21
to web-vitals-feedback
Dear Alekseys thank you very much for your information. Really strange, not every site with a cookie banner has a poor FID :(

Greetings Kathrin
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