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WKWebview termination due to memory. Adjustable threshold for termination?
Hi, Our company has an application uses the WKWebview to host a lot of content. The content is web based and hosts a lot of charts and metrics. Because of the high content, we've seen the memory of the WebContent hit above 1.25 GB. When that happens, it'll eventually terminate and we have our recovery code to reload the same page Seems like the limit is hidden / internal. Some Apple devs also noted something might be hard coded to be limited as well. Yes, we have our optimizations but we still need to keep our queries, use react, cache, etc... It's just a heavy web application. Request: Can you help us raise that limit? Are there some limitations in Webkit for such a need to terminate? As some devices have much higher RAM than before, we were hoping to be able to dynamically adjust the limit for the wkwebview before it resets. We contacted our internal contacts but they said to post here.
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505
Jan ’25
Simulator 18.4 Webview CORS issues
I have a very specific issue that happens only on iOS Simulator version 18.4. It does NOT happen when I run my app on a real iOS 18.4 device through Testflight. My app displays a WebView (courtesy of Capacitor, url scheme capacitor://). Inside that Webview I'm using Firebase JS API (11.2.0) and calling signInWithEmailAndPassword, which works well in all other contexts, i.e. browser, Android webview, iOS webview in all other Simulator versions, and on real devices. Only when running in Simulator 18.4, I get a failed network request: cannot parse response Fetch API cannot load https://identitytoolkit.googleapis.com/v1/accounts:signInWithPassword?... due to access control checks. Failed to load resource: cannot parse reponse error: FirebaseError: (auth/network-request-failed) Everything is working correctly for both: Capacitor app webview installed on a real 18.4 device with Testflight Safari (non-webview) in the 18.4 Simulator The issue is severe for us, because we are unable to develop our app and test it in the simulator on 18.4 Simulator before pushing it through Testflight internal release. Request headers on the failed request (no response status or headers available). Request Accept: / Content-Type: application/json Origin: capacitor://localhost Sec-Fetch-Dest: empty Sec-Fetch-Mode: cors Sec-Fetch-Site: cross-site User-Agent: Mozilla/5.0 (iPhone; CPU iPhone OS 18_4 like Mac OS X) - AppleWebKit/605.1.15 (KHTML, like Gecko) Mobile/15E148 X-Client-Version: Mobile/JsCore/11.2.0/FirebaseCore-web X-Firebase-Client: (...)
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279
Apr ’25
Smart Banner for Testflight App
Hi, I am wondering if anyone has experience with Smart Banners for an application not released on the app store, but still in TestFlight, specifically an AppClip. I am working on an exisiting project where a Smart Clip is used with a smart banner on the website for core functionality. Previously, even in test environment (app is in test flight and not app store) the smart banner would correctly show on the website and allow testers to launch the app clip experience, however this no longer seems to work. Its noted the test environment was last tested and deployed 2 years ago, and was working correctly, and there have been no changes to the website (the meta tag and .aasa file are all setup correctly). The only recent change was upgrading the app to support the latest iOS version, however beyond that no functionality in the app has changed. Apple developer support hasn't been very helpful, and reviewed our account and stated "everything appears to be running as expected on our end" Has something changed in Safari in that it no longer accepts test flight app smart banners, and if it doesn't, does anyone have any other suggestions? Cheers
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441
Jan ’25
WebGPU supporting in Safari on macOS
Hi, now we could try WebGPU by manually enabling it in feature flags in no matter Safari or Safari technology preview on macOS. But, do we know when this WebGPU feature would be enabled by default or any plan to enable it by default in Safari? Thanks!
Topic: Safari & Web SubTopic: General
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371
Feb ’25
App’s navigation bar items change background color unexpectedly
iPadOS 26, dark mode Open Safari Search for anything or open a website that has white background Kill Safari Open Safari again I still can reproduce it with Safari on iPadOS 26.0.1 This issue also happens to my app when opening a HTML/JS on WKWebView with white background while using dark mode. I did send a feedback ticket when using iPadOS 26 beta but havent seen any reply. This is my first time sending a feedback so I dont know if Apple would reply or not.
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269
Oct ’25
Missing Cookies in Set-Cookie Header in webRequest.onHeadersReceived callback in Safari Web Extension
We’re seeing an issue in our Safari Web Extension where not all cookies from the Set-Cookie response header are accessible. We are using macOS 15.4 and Safari 18.4. In the webRequest.onHeadersReceived callback, the Set-Cookie header returned by Safari only includes some of the cookies set by the server. If multiple Set-Cookie headers are present, we seem to receive only a partial list, some cookies are missing entirely. In Chrome and Firefox, the same callback provides all cookies set by the server without issue. We are looking for assistance in fixing these issues and having our Safari Extension function the same as it does in Firefox and Chrome.
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170
Apr ’25
Issues Observed with App Clip Behavior and URL Handling
Hi Apple Team, We’ve noticed a couple of issues with launching default App Clip in safari and would appreciate your guidance. App Clip Popup Timing: When launching the App Clip using default URL, we sometimes see the small App Clip popup appear before the App Clip banner is displayed. Ideally, the banner should appear first. Cached URL Handling: In certain cases, the App Clip appears to be using a cached URL instead of the most recent one. For example, when we invoke two different App Clip URLs with unique parameters, the App Clip sometimes launches using the previous URL’s data instead of the new one. This behavior is inconsistent and makes it difficult to ensure users are directed to the correct experience each time. Could you please help us understand whether this is expected behavior or if there are any known issues or recommended solutions? Thank you for your time and support. Example
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173
Oct ’25
WKWebView randomly does not send out cookies from WKWebSiteDataStore to our servers
PLATFORM AND VERSION iOS Development environment: Xcode 16.2, macOS 15.3.2 Run-time configuration: iOS 15-18 This happens in iOS, and leads to to the hybrid home page showing users as wrongly unauthenticated, since the at cookie is missing. For context, we have a JWT token that is stored in the Keychain, and on app launch, before any WKWebViews are created, we synchronize this to the WKWebsiteDataStore as an at cookie. We have analytics instrumentation on our websitef to show that WKWebView randomly refuses to send out any cookies. – The following is a snippet from an explanation to the WebKit Slack: We are having an issue on iOS, in which WKWebView loads pages (and even subsequent reloads) without any cookies, even though we have stored cookies in WKWebsiteDataStore.default() before hand right after application launch and becoming a key window. We reference this object, store it as a singleton, (as well as a process pool), and then all webview configurations are initialized with the same data store, the same process pool, every call on the main thread. From reading the source code, it seems that if the internal IPC logic fails, the APIs for deleting and setting data records and cookies fail without any feedback in completion handlers. This bug often happens when returning from the background on iOS after a few hours. Sometimes it happens on cold launches of the app. We have mitigated a similar issue (no cookies being sent) by implementing webViewWebContentProcessDidTerminate and reloading the webview ourselves, we found that whatever webview does to reload if that method is not implemented leads to cookies not being used. There have been multiple reports of WKWebView losing cookies in recent iOS versions, and we have tried to implement all of the workarounds listed. Setting a maximumAge to the cookies we store, and doing a _ = await websiteDataStore.dataRecords(ofTypes: Set([WKWebsiteDataTypeCookies])) before accessing or modifying websiteDataStore.httpCookieStore Question: is it safe to work with WKWebsiteDataStore before a WKWebView is added as a view, if so are there any timing considerations? Are there any logs that we can take a look at, this issue is very hard to reproduce, about 2% of our users face it at scale? Is there anything that could be happening within our process (runloop issues, timing) that could be causing this issue? See multiple reports from other companies that have faced the issue: "Now the Thermonuclear Problem with WKWebViewDataStorage" https://medium.com/axel-springer-tech/synchronization-of-native-and-webview-sessions-with-ios-9fe2199b44c9 STEPS TO REPRODUCE They don't exist, because the issue only happens at scale. We just know that no cookies are sent for a small percentage of requests. We believe this to be an issue in which Webkit fails to communicate internally with whatever IPC mechanisms it has. We have not been able to reproduce this issue consistently. The best we can give is that it happens after a few hours that the app is in the background. This happens regardless of whether the WKWebsiteDataStore is persistent or not, but seems to be much worse when it is persistent. Thus we have disabled persistnet data stores and relied on nonPersistent. The issue is bad enough that we are trying to move away from relying on cookies for iOS and just use request headers which we can only set on the top level request of WKWebView. DTS Case-ID: 13154329
Topic: Safari & Web SubTopic: General
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130
Apr ’25
Safari tabs lost updating to macOS 15.4
Problem As the title says, Safari lost all my tabs once I updated to macOS 15.4. I do of course have "Safari opens with: All windows from last session" set. This has been my default for many years. Past Mitigation In the past I had a script that I could use to backup ~/Library/Safari that would save all my bookmarks and tabs. Unfortunately they made this method of backup non-function sometime around when tab groups were introduced. Suggestion Fortunately my tab groups are still intact. But this sort of problem doesn't give me a lot of confidence. I haven't had something like this happen in a while, but when it does happen, it's quite frustrating. Apple really needs to recognize that this sort of thing can and will happen and they should make it easier for users to manually save/restore their tabs. Problem with forums To add insult to injury, as I was typing this message in the forum, I decided to select "Edit Bookmarks"... which proceeded to replace the current window with my bookmarks, thereby losing my post! It did this without warning of page content changes (which I get from most other websites). I felt somewhat relieved that the forum had recognized a previous draft and offered for me to continue. However, when I selected it, it brought me back to an old post... that was actually posted! smh
Topic: Safari & Web SubTopic: General Tags:
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Apr ’25
@@extension_id replacement in CSS file fails in Sequoia, Safari 18
Typically, you can use the @@extension_id special string to reference the absolute path into the bundled resources of an extension, such as an image or a custom font, in a CSS file. However, this broke with Safari 18. Consider this section in a popup.css file: .card-icon { height: 16px; width: 20px; background-image: url(safari-web-extension://__MSG_@@extension_id__/images/card.svg); background-size: 20px 16px; } In Safari 17.4, once loaded in the browser, @@extension_id is replaced with E8BEA491-9B80-45DB-8B20-3E586473BD47, and the background-image reads as so: background-image: url(safari-web-extension://E8BEA491-9B80-45DB-8B20-3E586473BD47/images/card.svg); But as of Safari 18, the @@extension_id just collapses to an empty string, and the background-image reads as so: background-image: url(safari-web-extension:///images/card.svg); and the svg fails to load with the following error: "Failed to load resource: You do not have permission to access the requested resource." This is a regression, does to match the behavior of the other major browsers, and should be fixed. Filed with Feedback ID: FB15104807
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809
Apr ’25
Safari extension service worker appears with a delay in the Develop dropdown
Hi, I'm developing an extension and I need to debug console logs that are logged in the Service Worker. The worker is configured in the manifest and is generally working as expected: However, when I open the browser, go to any site, and open Develop -> Service Workers or Develop -> Web Extension Background Content it is not visible there, so I can't really access the logs: But then I noticed that if I go out of focus from the browser for some time (and probably let the SW die), it becomes visible and I can open it without an issue: So, a couple of questions: Why isn't it instantly accessible? The extension Service Worker dev tools should be accessible regardless of what is happening to the tab or the browser, even if the SW terminates. Why does it eventually appear under Web Extension Background Content instead of the Service Workers when it is in fact an SW?
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426
Feb ’25
New IOS Safari CSS Issue with DVH & VH
After updating to the new iOS, in Safari, my overlays and backdrops using 100dvh no longer cover the full screen there's now a gap at the bottom. Switching to 100vh fixes it, but that causes scrolling issues on older Safari versions since 100vh includes extra height. Has anyone else experienced this? What's the recommended fix that works across iOS versions?
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343
Oct ’25
Concerning recent trend of start page bugs on Safari
Summary Recently a number of bugs affecting our Safari extension have been introduced with various Safari 18.X updates. We've submitted feedback for all of these, but most have received no response. We need to raise this to your attention as it has been affecting our developer experience and causing a lot of frustration for our users. It's something that adds a lot of uncertainty for us. These issues affect core web functionalities but seem to be isolated to the Start Page or Extension environments. For example: using window.open, no longer works using window.location.href = ... no longer works Including a tag in our start page causes infinite reloading to occur. registering a content script more than once will crash Safari Details Unable to open new window as as start page extension in Safari 18 FB15879470 What happens: Calling window.open does nothing. This broke our links to our feedback submission, marketing site & help site. When: Nov 18, 2024 - Initial launch of Safari 18 on macOS Status: Open, No response Unable to open app url scheme with window.location.href in start page extension in iOS 18 FB15879596 What happens: Changing the URL in this way does nothing (well actually it does work about 10% of the time). This broke our navigation to in app payment. When: Nov 18, 2024 - Initial launch of Safari 18 on iOS Status: Open, No response New tab extensions broken FB16126043 What happens: Having a tag in your causes an infinite loop of reloading the start page. This broke our entire start page extension. When: Dec 19, 2024 - Safari 18.3 on iOS beta Status: 10 similar tickets found, marked for future OS update. We did get a response and a fix is identified for a future release window.open opens “about:blank” when called from Start Page extension. FB16427985 What happens: calling window.open from the start page opens about blank on iOS 18.3. Similar to the first issue, but slightly different behaviour. This broke our links to our feedback submission, marketing site & help site. When: Jan 30, 2025 - Safari 18.3 Status: Open, No response Registering a content script more than once causes Safari to crash in macOS 15.4 beta FB16831768 What happens: We have an optional content script that we were registering every time it was used. Although somewhat redundant, it was much simpler than checking if one was already registered and tracking if an updated one needed to replace it. This works fine on all other browsers and all prior Safari versions we've released it on. However if a user enables site blocker on the latest version, as soon as they visit any website, our content script registration causes Safari to crash. Essentially preventing users from using Safari until they uninstall our extension. When: Mar 11, 2025 - Safari 18.4 Status: Open, No response In Conclusion Luckily we have been able to isolate and find workarounds for most of these issues so far, but we are not guaranteed to in the future. We are raising this not only to have these issues looked into, but to raise awareness of the rising trend of basic functionality of Safari extensions breaking with Safari updates. We hope that this can influence a shift in your QA & feedback intake practices to ensure these issues are less frequent in the future. We are happy to raise future issues through your provided channels as they are discovered. But to have our feedback ignored and then have to rely solely on workarounds to prevent disruptions to our users' experience is concerning. We submitted this feedback to our developer relations contact, and he suggested we submit a TSI to look into these issues. In response to this, we were advised to post this here.
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144
Apr ’25
WKWebView 120hz Support
I'm developing an application that needs smooth framerates within a wkwebview that interacts with native code. However, requestAnimationFrame by default is still throttled to 60hz even if all my target devices (the iPad Pro for example) have supported 120hz for a long time already. I noticed that the latest Safari in 18.3 beta supports unlocked framerates, but that's only under Safari feature flags. To my knowledge, these flags do not apply to WKWebView. Is there a way to enable unlocked framerate in WKWebView via requestAnimationFrame? (Calling JS at a faster rate from the native code side will not work, almost definitely, since WKWebView will still render at its own rate.) This is an experimental application for internal use and I'm okay if there are temporary beta solutions available.
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707
Jan ’25
Xcode 26 crash upon dealloc of `WKNavigationResponse` on Main Thread
Since Xcode 26 our tests are crashing due to the Main Thread not being able to deallocate WKNavigationResponse. Following an example: import Foundation import WebKit final class WKNavigationResponeMock: WKNavigationResponse { private let urlResponse: URLResponse override var response: URLResponse { urlResponse } init(urlResponse: URLResponse) { self.urlResponse = urlResponse super.init() } convenience init(httpUrlResponse: HTTPURLResponse) { self.init(urlResponse: httpUrlResponse) } convenience init?(url: URL, statusCode: Int) { guard let httpURLResponse = HTTPURLResponse(url: url, statusCode: statusCode, httpVersion: nil, headerFields: nil) else { return nil } self.init(httpUrlResponse: httpURLResponse) } } import WebKit import XCTest final class ExampleTests: XCTestCase { @MainActor func testAllocAndDeallocWKNavigationResponse() { let expectedURL = URL(string: "https://galaxus.ch/")! let expectedStatusCode = 404 let instance = WKNavigationResponeMock() // here it should dealloc/deinit `instance` automatically } Here the call stack: Thread 0 Crashed:: Dispatch queue: com.apple.main-thread 0 CoreFoundation 0x101f3dd54 CFRetain.cold.1 + 16 1 CoreFoundation 0x101e14860 CFRetain + 104 2 WebKit 0x10864dd24 -[WKNavigationResponse dealloc] + 52
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1.2k
Oct ’25
Safari extension doesn't load
I don't know why but all of a sudden when I build the extension it just doesn't load in Safari. The build executes fine but the extension doesn't load. Sometimes, through trying different combinations of clearing the build folder, building, archiving, ... it suddenly loads. And the next time I build again it doesn't load properly. So I can't do any work on it or test anything. I don't know why all of a sudden I am getting this behavior. It looks like engineers at Apple are constantly trying to overcomplicate a process that is at least ten times simpler in any other browser. This is ridiculous. Is this what our annual fee goes to? And they don't even provide any support for that. Several times I've tried to get some help here just to have to spend hours upon hours to figure it out by myself. I'm so tired of this.
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249
Apr ’25
WebGL is crashing in IOS 18.2 and 18.3
Hello, We’ve been using the CesiumJS WebGL library for several years, both on our website and within embedded WebViews in our iOS application. Since upgrading to iOS versions 18.2 and 18.3, we’ve started receiving numerous user complaints regarding application crashes on various iPad and iPhone models when loading CesiumJS. The crashes occur as soon as the 3D view initializes, and the error consistently reported is: "WebGL context lost" This issue appears to be a WebGL-related crash potentially triggered by GPU memory handling or allocation limits. However, we are not detecting any abnormal memory consumption prior to the crash, and the same setup works perfect on older iOS versions and on all Android devices and versions. Steps to Reproduce: Open: https://www.flightradar24.com/30.47,-94.84/8 Click on any aircraft icon on the map. In the aircraft details panel at the bottom, click on the “3D view” tab. On iOS 18.2 or 18.3, the page will crash shortly after initializing CesiumJS WebGL. Affected Devices: This issue is occurring across a wide range of devices, including: iPad 9th Generation iPad Pro (11-inch, 2nd Gen) iPhone SE (2020 and 2022) iPhone 11, 11 Pro iPhone XR iPhone Mini All of the above are running iOS 18.2 or 18.3. The problem does not occur on Android or previous iOS versions. Request: Has anyone else encountered similar issues with WebGL context loss after upgrading to iOS 18.2 or 18.3? Are there any known changes in memory limits or WebGL behavior in these recent iOS updates? We’d appreciate any insight or suggestions on workarounds or potential fixes. Thank you!
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Mar ’25