Safari Lockdown Mode

[nihil-admirari]

Lockdown Mode disables certain web technologies. It may be worthwhile to document which ones are disabled.

For example, WAV, FLAC, and OPUS (both in CAF and MP4) audio formats no longer work (tested with https://hpr.dogphilosophy.net/test/, also see #6805).

[nihil-admirari]

Image testing (https://wiesmann.codiferes.net/share/bitmaps/): PDF, TIFF, BMP, AVIF, JPEG2000 are not supported in lockdown mode. New JPEG XL is also not supported.

https://www.sevarg.net/2022/07/20/ios16-lockdown-mode-browser-analysis/ says the following technologies are also disabled:

• WebRTC
• WebGL
• GamePad API
• MathML
• Speech Recognition API
• Web Audio API

[jensimmons]

There is also information available in Safari release notes about what is newly disabled by Lockdown mode with each release.

If Can I Use wants to document Lock Down Mode changes, we'd like to help figure out the best design for this information.

[nihil-admirari]

Are there separate release notes for iOS Safari?

I'm asking since I've opened this issue after investigating Opus support (#6805), which is different on macOS and iOS. Safari 17 Release Notes says:

Added support for stereo-only Opus in MPEG-4 and WebM containers on macOS Sonoma. (50994465)

Opus in WebM doesn't play on iOS, but Opus in MP4 apparently does (unless Lockdown mode is enabled).

What is disabled in Lockdown mode on iOS may also differ from what is disabled on macOS.

[jensimmons]

There is one set of release notes for Safari and WebKit, not separate release notes for macOS, iOS, iPadOS, visionOS, or watchOS. If a particular web technology has different support on different platforms, we'll note it. Otherwise, assume the release note applies to all platforms.

[hugmouse]

Found this commit: WebKit/WebKit@4963017#diff-3ce474a02de25f38af60ea948ab73b01edf0841afde13c6fc6f7eeaa05531c56

Helps to understand what is EXACTLY is disabled in Lockdown mode.

Little bit detail on PDF rendering: https://github.com/WebKit/WebKit/blob/7e6961eb5e70f087ab063b6f4656b79348c3bf0e/Source/WebKit/WebProcess/WebPage/Cocoa/WebPageCocoa.mm#L129-L139

On remote fonts: https://github.com/WebKit/WebKit/blob/7e6961eb5e70f087ab063b6f4656b79348c3bf0e/Source/WebCore/css/FontFaceSet.cpp#L169-L192