Userscripts is a Safari browser extension that installs and runs custom JavaScript and CSS on websites through Apple's content script injection system. It provides a privileged execution context that allows userscripts to perform cross-origin HTTP requests and access clipboard functionality beyond standard browser sandbox restrictions.
The extension uses metadata tags like @match, @run-at, and @weight to control precisely when and where scripts execute on web pages. It includes a built-in code editor with syntax highlighting and linting for modifying scripts directly, and supports automatic synchronization of local scripts with newer versions from configured remote URLs using @updateURL metadata.
Scripts are stored as files in a user-selected filesystem directory, enabling external editing and version control. The extension also provides per-script persistent key-value storage across browser sessions, dynamic CSS injection via GM.addStyle, and programmatic tab management from within userscripts. It is installed through Apple's App Store on iOS 15.1+ and macOS 12+ with Safari 14.1+.
