Simple Cross Browser Suspender Extension

Summary

A cross-browser extension to suspend inactive / unused tabs by "hiding" them behind a static, generic browser error page. Basically to suspend https://moshe-gr.com, it will be redirected to http://localhost:0/#https://www.moshe-gr.com (try it ;) ).

Background

The great suspender (RIP).

• In much more detail.

My own TL;DR

The great suspender was an extension that would automatically replace an open tab with a static, low memory page that would redirect back to the original on demand or after a set idle time. After a change of ownership, it was abused to contain malware, and therefore removed by Google.

Looking to avoid another extension by and unknown developer (who can always change), I opted to find a safer solution. I believe I have found it and want to share it in a way that can let others use / replicate it for their own benefit, at the level of knowledge and safety they require.

Why is this solution safer

• No static page - cannot be abused without changing the logic in a noticeable way.

• Hash parameter - not sent to a server by the browser, by design.

• I decided to use localhost:0 as a "host" to keep things local, and on a port that shouldn't conflict with other services / local servers.

  • See why here.

• Simple code base - easy to fork, install manually, and if necessary - replicate.

  • The core of the script boils down to:

    const suspendPrefix = "https://localhost:0/#";
    const toggleSuspendUrl = (pageUrl) =>
      pageUrl.startsWith(suspendPrefix)
        ? pageUrl.replace(suspendPrefix, "")
        : `${suspendPrefix}${pageUrl}`;
    if (browser) {
      browser.browserAction.onClicked.addListener((tab) => {
        browser.tabs.update(tab.id, { url: toggleSuspendUrl(tab.url) });
      });
    }

• The API I'm using doesn't require running Javascript code on the web page in the tab - just to get a page's URL. This makes the abuse potential minimal, and is reflected in the extensions limited permissions.

• Advanced features, if/when added, will be "opt in" via a separate installation (on stores if / when I upload them) and branch (or possibly repository) - to always provide a stable, simple, and secure base version.

Known issues

• Cannot unsuspend internal pages in Mozilla, due to the following issue.

Resources for Potentially Relevant APIs

• Awesome resources.

Cross Browser APIs

• Firefox general notes.

Base capability - read URL + redirect manually

• Tabs API.
  • Move tab to a new URL - tabs.update().
  • discarded tabs - as documented here.
• Windows API.
  • Get window URL - windows.getCurrent().
    • Example extension.
• Call via a page action.

Add on features (will be a separate branch + extension)

• Schedule code to run at a specific time in the future using the alarm API.
• Idle recognition via the idle API.

Incompatabilies

• By Firefox.

Examples

• Firefox Examples.
• Porting from Google Chrome.
• Tutorial.

Mobile

• Firefox Docs.

Handling error pages in browsers (current solution works without this)

Chrome error pages take over the window.location.href attribute https://stackoverflow.com/questions/29989031/getting-the-current-domain-name-in-chrome-when-the-page-fails-to-load

I used a different selector when trying to run code from the page (not the current solution - recorded here in case it is needed):

document.querySelector(`[jscontent="failedUrl"]`)?.innerText;