Why Do `window.close()` and `self.close()` Fail to Close Chrome Windows?

Window.close and Self.close Failing to Close Chrome Windows: A Comprehensive Analysis

Invoking window.close() or self.close() within JavaScript code may fail to close the window in Chrome. This discrepancy stems from a common misconception that Chrome prohibits scripts from closing windows unless they were script-created. While this is false, these methods may still fail to function as expected. This article delves into the underlying reasons and explores potential solutions.

Security Restrictions

Modern browsers have implemented security measures to prevent malicious scripts from closing windows indiscriminately. As per the window.close() specification, JavaScript is generally not allowed to close a window that was not created by the same script. This restriction aims to curb security exploits and user inconvenience.

Firefox Implementation

Firefox strictly adheres to these security guidelines, explicitly prohibiting scripts from closing windows that were not opened by script. If a Greasemonkey/Tampermonkey script attempts to use window.close() in Firefox, it will trigger the error message: "Scripts may not close windows that were not opened by script."

Chrome Implementation

Chrome, on the other hand, allows scripts to close windows that were not script-created. However, this exception does not extend to userscript contexts like Greasemonkey or Tampermonkey. Attempts to use window.close() from these contexts will result in silent failure.

Workarounds

While Chrome extensions and Firefox add-ons provide a reliable solution for closing windows, there are hacky workarounds for user scripts:

Chrome:

• Self Redirection Exploit: This exploit is no longer effective in general. However, it may still work with injected code in newly opened tabs with no browsing history.
• @grant Window.Close Method: Using the @grant directive in Tampermonkey scripts, it is possible to enable window.close() functionality. However, this only works for additional tabs and not for the last remaining tab.

Firefox:

• Disable Security Settings: Alter the about:config setting allow_scripts_to_close_windows to true. This is not recommended due to security concerns.

Long-Term Solution

The most reliable approach is to create a dedicated Chrome extension or Firefox add-on that can invoke window.close() effectively. Alternatively, user script developers could consider submitting a feature request to Greasemonkey or Tampermonkey for built-in window closing functionality.

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