Created attachment 407183 [details] testcase ## Environments * Safari 14 on Big Sur beta 5 * Safari TP 112 on that is also reproducible. ## Step to Reproduce 1. Extract testcase.zip. 2. Run `python -m SimpleHTTPServer` 3. Open Safari and open safari’s developer tools’ network pane. 4. Open index.html via launched in _step 2_. ## Expected Result For images, Safari requests only `example_webp.webp`. ## Actual Result For images Safari requests both of `example_webp.webp` and `example_png.png` Sadly, today’s website use react or other view libraries to conceal an actual DOM manipluations. Their library are sometimes used to “hydrates” web page on static html served by a server-side, then this kind of bugs causes multiple undesired image requests accidentally. With webbev’s hat, the combination of `<picture/>` and `<source type="image/webp"/>` are used as progressive enhancement techniques to use WebP images for supported browsers to reduce network bandwidth. So this kind of bugs are not desired behavior.
I seem bug 159484 and bug 177068 are similar but I'm not sure about they are duplicated of this.
<rdar://problem/68135403>
This is the same as bug 159484. They both address the issue of loading multiple resources for the same <picture> element although a single resource will be displayed at the end. *** This bug has been marked as a duplicate of bug 159484 ***