It’s both a joy and a curse that so many tell me of bugs they encounter. The joy is that it enables me to investigate and report them here, but the curse is when I can’t reproduce the problem. This week’s curse has been Safari’s webarchives, a topic that I had wisely avoided for several years. Search this blog using the tool at the top right of any page and you’ll see just four articles here that mention webarchives, and this is now the second in the last ten days.

While I’m writing about searching this blog, I should point out that tool doesn’t take you out to Google or any general search engine, but confines its scope to articles published here. Although precious few seem to use it, I find it invaluable when preparing articles, and strongly recommend it.

Not only had I avoided tackling this topic, but I see from my own local search that I have seldom used webarchives myself, although not as a result of any unreliability.

In principle, Safari’s webarchives should rarely cause a problem. They’re written by converting what Safari already holds in memory for a webpage into an XML property list, a process termed serialisation, and used effectively by a great many apps in more challenging circumstances. There may be occasions when this doesn’t quite work right, and it does require Safari to retain backward compatibility to ensure it can load and display property lists written some years ago. But by and large it should prove robust.

In practice, there are quite a few who appear unable to get this to work with many versions of Safari, yet I can’t repeat that here. For one reader, the most recent version of Safari that can reliably open their webarchives is 18.6, which is the only version I have experienced problems with. Running in macOS Ventura 13.7.8 here, that version appears unable to open the webarchives it creates, or those from later versions of Safari. Meanwhile Safari 26.1 running in macOS 26.1 has no trouble opening any webarchive I’ve tried from 2009 onwards.

For the last three years, Safari and its supporting libraries including WebKit have been provided to macOS in a cryptex, where they can’t be modified. The only way the user can go beyond Safari’s settings to change its behaviour is using Safari Extensions, which are controlled by Apple. There doesn’t appear to be any way for the user to prevent WebKit and Safari from loading webarchives correctly, intentionally or inadvertently.

Cursed by my inability to reproduce the problems reported, I have immersed myself in a couple of lengthy log extracts. One documents Safari 18.6 failing to open a webarchive it created, the other shows Safari 26.1 successfully opening the same webarchive.

Safari 18.6 seems to have been making good progress opening the webarchive until it came to loading the main frame. It then needed PolicyForNavigationAction before it could go any further:
01.154639 com.apple.WebKit Loading Safari WebKit 0x14c19b818 - [pageProxyID=21, webPageID=22, PID=596] WebPageProxy::decidePolicyForNavigationAction: listener called: frameID=24, isMainFrame=1, navigationID=26, policyAction=0, safeBrowsingWarning=0, isAppBoundDomain=0, wasNavigationIntercepted=0
01.154642 com.apple.WebKit Loading Safari WebKit 0x14c19b818 - [pageProxyID=21, webPageID=22, PID=596] WebPageProxy::receivedNavigationActionPolicyDecision: frameID=24, isMainFrame=1, navigationID=26, policyAction=0
01.154666 com.apple.WebKit Loading Safari WebKit 0x14c19b818 - [pageProxyID=21, webPageID=22, PID=596] WebPageProxy::isQuarantinedAndNotUserApproved: failed to initialize quarantine file with path.
01.154666 com.apple.WebKit Loading Safari WebKit 0x14c19b818 - [pageProxyID=21, webPageID=22, PID=596] WebPageProxy::receivedNavigationActionPolicyDecision: file cannot be opened because it is from an unidentified developer.
01.154799 Error Safari Safari Web view (pid: 596) did fail provisional navigation (Error Domain=NSURLErrorDomain Code=-999 "(null)")

So loading the main frame was halted with those chilling words “file cannot be opened because it is from an unidentified developer”, with which we’re only too familiar. The webarchive was in quarantine, it seems, and that put a stop to its loading. Only that isn’t quite accurate: there was no com.apple.quarantine xattr present, but one of those ubiquitous com.apple.macl xattrs instead. Safari had been stopped by its own security, didn’t even have the courtesy to inform us, and just sat there with an empty window going nowhere.

Safari 26.1 shows how it should have been done:
00.740168 com.apple.WebKit 0xa4bda0718 - [pageProxyID=19, webPageID=20, PID=1035] WebPageProxy::decidePolicyForNavigationAction: listener called: frameID=4294967298, isMainFrame=1, navigationID=25, policyAction=Use, isAppBoundDomain=0, wasNavigationIntercepted=0
00.740172 com.apple.WebKit 0xa4bda0718 - [pageProxyID=19, webPageID=20, PID=1035] WebPageProxy::receivedNavigationActionPolicyDecision: frameID=4294967298, isMainFrame=1, navigationID=25, policyAction=Use
00.740233 com.apple.WebKit 0xa4bda0718 - [pageProxyID=19, webPageID=20, PID=1035] WebPageProxy::receivedNavigationActionPolicyDecision: Swapping in non-persistent websiteDataStore for web archive.

From then, WebKit moves apace and the archived webpage is soon displayed.

This doesn’t of course mean that Safari’s failures to open and display webarchives successfully are all the result of NavigationActionPolicyDecisions that the webarchive can’t be opened because of this security problem, but I suspect this isn’t the only time this has occurred. The vagaries of com.apple.macl xattrs are well known, and their propensity to cause other innocent actions to be blocked is only too familiar. Unfortunately, the only reliable workaround is to knock a hole through macOS security by disabling SIP. But for this to happen without any information being displayed to the user is unforgivable.

Other apps that access Safari’s webarchives don’t appear tainted by this behaviour. Michael Tsai of C-Command Software tells me that his EagleFiler app hasn’t had such problems since its introduction in 2006. If you’ve been struggling to open webarchives in Safari, you might like to consider whether that could address those problems. In the meantime, I can see what I’ll be doing over Christmas.

I’m very grateful to Michael Tsai of C-Command Software for information and discussion.

Websites come and go, and although the Internet Archive’s Wayback Machine provides a unique service by preserving so many, saving your own copies of pages remains important to many of us. This article looks at how you can do that using Safari 26, the current release for supported versions of macOS. If you want to explore the pages saved in the Wayback Machine, then its Safari extension is available free in the App Store.

Safari now offers the following five options for saving a page:

• File/Save As…/Page Source to save it as an HTML source file (169 KB).
• File/Save As…/Web Archive to save it as a Webarchive file (2.7 MB).
• File/Save As…/PNG to save it as a PNG image (43.5 MB).
• File/Export As PDF… to save it as a PDF file, in display format (31.6 MB).
• File/Print…/Save as PDF to save it as a PDF file, in print format (28.1 MB).

Sizes given are those for a test page with plenty of images from here.

Page source

This is the smallest and least complete version of the five, as it contains just the HTML source of the page, omitting all linked and similar generated content. For relatively plain pages containing text exclusively, this can be useful. The saved file can be opened in Safari or another browser, and so long as none of the linked content is missing or changed, you should see the original content reconstituted, but in a flattened layout without columns or styling. This is unlikely to be suitable as a lasting record, although it’s by far the most compact at 169 KB for the test page.

Web Archive

This saves to a single opaque webarchive file containing the entire contents of the page, including embedded images and other content, but not linked downloadable files. Although this format is peculiar to Safari, it has had limited support by some other apps, but I can’t find any other current software that can give access to its contents.

A webarchive file is a (binary) property list written as a serialisation of the web page content in Safari, in a series of WebResource objects. For example, a JPEG image would consist of:

• WebResourceData in Base-64 containing the image data;
• WebResourceMIMEType of image/jpeg;
• WebResourceResponse in Base-64 data;
• WebResourceURL containing the URL to the file.

Although in theory it should be possible to recover some of its contents separately, in practice that isn’t available at present. In the past access has been supported by the macOS API, but all those calls to work with Webarchive files are now marked as being deprecated by Apple. Current API support is limited to writing but not reading them from WKWebView from macOS 11 onwards, and there’s no sign of that being extended.

Webarchive format has changed over time, and compatibility with different versions of Safari is unpredictable. When testing in virtual machines, Safari 18.6 proved incapable of opening any webarchive test file, including its own, while Safari 26.0 and 26.1 loaded webarchives written by Safari 18.6, 26.0 and 26.1. There has also been a long history of problems reported with webarchive files. Recent versions of macOS can display QuickLook thumbnails and previews of webarchives, although thumbnails aren’t particularly faithful to their contents.

Although webarchives should contain embedded images shown in the original page, those appear to be saved at the resolution they’re displayed in. This helps limit the size of files; in the case of the test page used here, that required 2.7 MB, around 10% of the size of a PDF, making them the most efficient option apart from plain HTML.

When they work, Safari Web Archives can provide excellent snapshots of web pages, but longer-term compatibility concerns make them unsuitable for archival use.

PNG

Saving the page to a PNG graphics file is a relatively new option in Safari. For the example page, that generates a 2,622 x 32,364 pixel image of 43.5 MB size, making it the largest of all.

The PNG image is a faithful replica of the page as viewed, although it can be affected by lazy loading (see below). Disappointingly, its text contents don’t appear to be accessible to Live Text, limiting its usefulness.

PDF

Safari provides two routes for turning a webpage into a PDF document: directly using the Export As PDF… menu command, and indirectly via the Print… command then saving as PDF from the Print dialog. The results are different.

Exporting as PDF creates a document in which the entire web page is on a single PDF page, although it can spill over to one or two additional pages. The advantage of this is that the PDF is one continuous page without any breaks, and is a faithful representation of what you see in your browser, complete with its original layout and frames. The disadvantage is that this won’t print at all well, imposing page breaks in the most awkward of places. Very long pages can also prove ungainly, and difficult to manipulate in PDF utilities. The example page was 31.6 MB in size.

Printing to PDF breaks up the web page into printable pages, and splits up frames. What you end up with isn’t what you see online, but could at a push be reassembled into something close to the original. That isn’t too bad when the placement of frames isn’t important to their reading, but if two adjacent columns need to appear next to one another, this layout is likely to disappoint. It is the best, though, for printing, with headers and footers and page numbering as well. The example page was slightly smaller than the single-page version, at 28.1 MB.

While PDF is one of the preferred formats for archiving laid-out documents, it’s worth bearing in mind that standard macOS PDF isn’t compliant with any of the PDF/A standards for archival documents. You’d need a high-end PDF editor such as Adobe’s Acrobat (Pro) CC to prepare and save to any of those.

Despite being ancient and inefficient, PDF normally does a good job of preserving the original format and layout. Text content is preserved, if laid out erratically, making it ideal for content search. Thus, either of the PDF options is best-suited for archiving web pages from Safari.

Lazy loading

Recent versions of Safari appear to load pages lazily, only inserting some images and other included content when scrolled. If you save that page to PNG or PDF without scrolling to the end of the page, the resulting file may skip those images that haven’t yet been loaded. Check the file when it has been saved to ensure that all enclosures have been captured successfully.

Conclusions

• Save As…/Page Source is of limited use, mainly for text-only pages without embedded content.
• Save As…/Web Archive can be excellent for day-to-day use, being complete and faithful, but isn’t an open standard and can prove fragile. It’s therefore not recommended for critical or archival use.
• Save As…/PNG is of limited use, as its images are largest and their content least accessible.
• Export As PDF… is excellent for day-to-day use, complete and faithful, but for serious archival use needs to be converted to comply with an archival standard in the PDF/A series.
• Print…/Save as PDF is an alternative more suitable if you want to print the document out.
• Before saving to PDF or PNG ensure you scroll through the whole page, then afterwards check the saved document contains everything it should.