298222 2025-09-02 03:06:55 -0700 REGRESSION (iOS 18.6): Page load takes ~24s in Safari/WebView 2025-09-02 11:21:41 -0700 1 1 1 Unclassified WebKit CSS WebKit Nightly Build All Other RESOLVED DUPLICATE 297591 dentsplysirona.com/de-de InRadar, Performance P1 Critical --- 1 neetu.a.rani webkit-unassigned bfulgham deepak.srivastava ganesh.muddliyar koivisto neetu.a.rani simon.fraser webkit-bug-importer zalan oldest_to_newest 2140185 0 neetu.a.rani 2025-09-02 03:06:55 -0700 Product: WebKit (Safari / iOS) Version: iOS 18.6 (WebKit 618.x – exact version if possible) Hardware: iPhone 14 / iOS 18.6 (also reproducible on other iPhones) Steps to Reproduce Open Safari on iOS 18.6 (or any WKWebView in an app). Navigate to [dentsplysirona.com/de-de] Observe load time and rendering. Expected Results Page loads in ~2–3 seconds (normal load time on iOS 18.5 and earlier). Layout renders progressively, no long blocking tasks. Actual Results Page takes ~24 seconds to fully load. Rendering stalls before first paint. Same page on iOS 18.5 loads quickly, so this appears to be a regression introduced in 18.6. Additional Notes- Issue affects both Safari and in-app WebViews (WKWebView). Desktop Safari 18 (macOS) does not show this issue. Clearing cache/cookies does not help. Happens consistently across multiple sites with moderate JavaScript and CSS payloads. Possibly related to JS parsing/render pipeline regression introduced in iOS 18.6. 2140187 1 neetu.a.rani 2025-09-02 04:25:53 -0700 Hi emilio@crisal.io are there any updates? 2140244 2 ap 2025-09-02 08:37:56 -0700 *** Bug 298226 has been marked as a duplicate of this bug. *** 2140245 3 ap 2025-09-02 08:41:13 -0700 I can reproduce that the page loads quickly in iOS 18.4.1 (don't have 18.5 handy). Both iOS 26 and macOS 26 show the same issue which is similar to one reported, except that the page does get some content painted before stalling. 2140246 4 webkit-bug-importer 2025-09-02 08:41:23 -0700 <rdar://problem/159670991> 2140255 5 ganesh.muddliyar 2025-09-02 09:04:59 -0700 Do we know by when this will be fixed? 2140297 6 simon.fraser 2025-09-02 10:48:47 -0700 The page is spending a lot of time in CSS selector code: 2405 ??? (in <unknown binary>) [0x10f644044] 2405 WebCore::jsDOMTokenListPrototypeFunction_add(JSC::JSGlobalObject*, JSC::CallFrame*) (in WebCore) + 228 [0x1b54577c4] 2405 WebCore::DOMTokenList::addInternal(std::span<WTF::AtomString const, 18446744073709551615ul>) (in WebCore) + 332 [0x1b6b2bd28] 2405 WebCore::DOMTokenList::updateAssociatedAttributeFromTokens() (in WebCore) + 612 [0x1b6b2c6c0] 2405 WebCore::Element::setAttribute(WebCore::QualifiedName const&, WTF::AtomString const&, bool) (in WebCore) + 264 [0x1b68f2fb8] 2405 WebCore::Element::setAttributeInternal(unsigned int, WebCore::QualifiedName const&, WTF::AtomString const&, WebCore::Element::InSynchronizationOfLazyAttribute) (in WebCore) + 564 [0x1b68fda04] 1338 WebCore::Style::AttributeChangeInvalidation::invalidateStyle(WebCore::QualifiedName const&, WTF::AtomString const&, WTF::AtomString const&) (in WebCore) + 3656 [0x1b7984128] ! 1127 WebCore::CSSSelectorList::makeJoining(WebCore::CSSSelectorList const&, WebCore::CSSSelectorList const&) (in WebCore) + 200 [0x1b66454c0] ! : 714 WebCore::CSSSelector::CSSSelector(WebCore::CSSSelector const&) (in WebCore) + 212,216,... [0x1b4ca3290,0x1b4ca3294,...] ! : 413 WebCore::CSSSelector::CSSSelector(WebCore::CSSSelector const&) (in WebCore) + 232 [0x1b4ca32a4] ! : 321 WTF::fastMalloc(unsigned long) (in JavaScriptCore) + 396,12,... [0x1b098049c,0x1b098031c,...] ! : 49 bmalloc_allocate_casual (in JavaScriptCore) + 72 [0x1b221fe94] 2140312 7 simon.fraser 2025-09-02 11:21:41 -0700 This was fixed in 299018@main. *** This bug has been marked as a duplicate of bug 297591 ***