Features Disabled by iOS 16 Lockdown Mode

Apple introduced Lockdown Mode in iOS 16 as an extreme, optional protection designed for individuals who might be personally targeted by sophisticated digital threats like mercenary spyware. When activated, the feature dramatically reduces the device's attack surface by strictly limiting or entirely shutting down specific system capabilities, web technologies, and communication protocols. This article details the exact system capabilities and web features that are disabled or restricted when Lockdown Mode is enabled on an iPhone running iOS 16.

Web Browsing Restrictions

Lockdown Mode applies strict security measures to Safari and all other WebKit-based browsers on iOS:

  • Just-In-Time (JIT) JavaScript Compilation: JIT compilation is completely disabled, which slows down JavaScript execution on complex sites but closes off a major vector for remote code execution. Users must manually exclude trusted sites to re-enable standard browsing speeds.
  • Complex Web Technologies: Several complex web features, including WebGL, WebAssembly, specific web fonts, and mathematical markup (MathML), are blocked.
  • Link Previews: Automatic rich previews for links loaded in browsers or messaging interfaces are suppressed to prevent unauthorized data fetching.

Messages

The Messages app faces heavy restrictions to neutralize zero-click exploits:

  • Message Attachments: Most message attachment types other than standard images (such as JPEG, PNG, and GIF) are blocked. Audio, video, and document files cannot be received automatically.
  • Link Previews: Rich link previews are disabled within message threads to prevent the device from contacting untrusted servers without user interaction.

Incoming Calls and Apple Services

Lockdown Mode filters incoming communications to only allow interactions initiated by the user:

  • FaceTime and Calls: Incoming FaceTime calls and service requests are automatically blocked unless the user previously called or messaged that person or contact.
  • Shared Photo Albums: Shared albums are completely removed from the Photos app, and invitations to join new shared albums are automatically declined.

Device Connections

Physical security measures are hardened to prevent hardware-based extraction and exploitation tools:

  • Wired Accessories: Wired connections to computers and USB accessories are disabled when the iPhone is locked. To allow an accessory or computer to connect, the user must explicitly unlock the device first.

Device Profiles and Enterprise Management

  • Configuration Profiles: Users cannot install custom configuration profiles, preventing malicious or unauthorized profiles from altering network routing or device trust stores.
  • Mobile Device Management (MDM): The device cannot be enrolled in Mobile Device Management while Lockdown Mode is enabled.