How Safari's Per-Site Extension Permissions Work

This article explores the per-site permission model for extensions in Apple's Safari web browser. It explains how the browser protects user privacy by restricting extension access by default, and details the exact mechanisms that allow users to grant temporary one-day access or permanently limit extension functionality to specific website domains.

The Architecture of Safari Extension Permissions

Safari utilizes a strict sandboxing model for web extensions. Even if an extension is programmed to read and modify data on every webpage a user visits, Safari blocks this capability upon installation. Instead of granting blanket permissions at the time of download, Safari intercepts the extension's request to access webpage content and defers the decision to the user on a site-by-site basis.

For an extension to read data, inject scripts, or alter the appearance of a webpage, the browser's underlying engine (WebKit) must verify that the user has explicitly authorized the extension to run on the active URL's domain.

How the "Allow for One Day" Feature Works

When a user interacts with an extension icon in the Safari toolbar on a new website, Safari presents a native system prompt asking how much access to grant. Selecting "Allow for One Day" triggers a temporary authorization process:

  1. Domain and Timestamp Logging: Safari records the specific domain of the active tab (for example, wikipedia.org) and associates it with the extension's unique identifier in a local permissions database. Simultaneously, it logs the exact timestamp of the approval.
  2. Script Injection: Once logged, WebKit immediately allows the extension to inject its content scripts and access the webpage's Document Object Model (DOM).
  3. Automatic Expiration: Safari continuously evaluates the timestamp against the system clock. Exactly 24 hours after the permission was granted, the temporary rule expires. Safari automatically purges the approval, blocks the extension from running on subsequent loads of that domain, and resets the permission state back to "Ask."

This allows users to utilize tools—such as coupon finders or page translators—for a single shopping or browsing session without giving those extensions permanent surveillance capabilities over their future activity on that site.

How Specific Domain Access Works

If a user wants an extension to work seamlessly on a trusted site without daily prompts, they can grant permanent domain-specific access. This is achieved by selecting "Always Allow on This Website" from the permission prompt.

  1. Permanent Allowlisting: Safari writes the base domain to a persistent allowlist tied specifically to that extension.
  2. Subdomain Inclusion: By default, granting access to a base domain also grants access to its subdomains, ensuring the extension works across the entire service.
  3. Navigation Verification: Every time the user navigates to a new URL, Safari checks the destination domain against the extension's allowlist before the page finishes loading. If a match is found, the extension runs automatically. If the user clicks a link that takes them to an external, unapproved domain, Safari immediately halts the extension's access for that new page.

Managing Permissions Manually

Users do not have to wait for a prompt to configure these settings. Safari provides a centralized dashboard to manage domain-specific rules:

  • Via the Address Bar: Clicking the puzzle piece icon or the specific extension icon in the toolbar allows users to change the current site's permission level on the fly.
  • Via Safari Settings: By opening Safari Settings (or Preferences) and navigating to the Extensions tab, users can click "Edit Websites." This reveals a list of all previously visited domains where permissions were configured. Users can manually switch any domain's setting between Ask, Deny, and Allow.
  • Via the Websites Tab: Under the Websites tab in Settings, users can select an extension from the sidebar and configure permissions for all currently open tabs at once, or set the default behavior for all unvisited websites.