I see this one showed up without any delay, probably because it did not have links. So I will paste below the previous message, just without links:

Hi Paul,
I am really enjoying your minimalistic theme, but while working on my website I noticed that performance in Safari is terrible when compared to any other browser. Let me explain in more detail.

Website address is: sochacki.info
I am on WordPress 5.6, but it was the same on 5.5

A while ago I also asked you how to remove the 2100px limit on photos, and implemented your suggestions:
mauer.co/topic/removing-2100px-size-limit-on-photos/

I admit that my website is heavy because I decided to upload 4000px photos to make them look good on 4K screens. I use RIOT and JPEGMini to optimise the photos, so they are not terribly heavy for their size and quality, but still, a page with 20 high res photos is not the easiest to render.

However, I checked the performance on a few computers, including a 2013 Macbook Air, 2019 Macbook Pro and my workstation PC, and I am happy with the results on all of them, except when Safari is used.

I tried Chrome, Firefox, Opera, Edge and Safari, and all the other ones work fine, but Safari really struggles.

I made a video showing the behaviour:
youtu.be/xutKBrAvy2U

As soon as I load a portfolio page on Safari the CPU usage goes to ~100% and I can start hearing the fans. Opening and closing Photoswipe, switching fullscreen on/off, going through the pictures, all those actions are quite laggy. Unfortunately Quicktime does not record mouse clicks, so it is not clear when I clicked on the video, but I had to wait for some actions for a few seconds. Everything was instant on Chrome.

This video was recorded on a Macbook Pro with Intel i9 CPU, I don’t have another Mac to test now, but I did test it before and on older computers it was even worse.

I was wondering if I broke something when making those modifications to remove 2100px limit. Before I made this topic I quickly installed a brand new WordPress, got the latest version of your theme, did not make any modifications, created one portfolio page, uploaded the pictures again and I had the same issues. This was only a local instal using Docker so I can’t give you a link to that test page. BTW. I noticed that pictures were not resized to 2100px on that new install, did something change?

Anyway, do you have any idea what it could be?

I would like to commit more time to my website, but I don’t want to work on it if the experience on Safari is so bad and I might have to re-do things.

Thanks!