Audible Tabs: Why Playing Sound Blocks Suspension

## Why it matters

A tab playing music, a video, or a call is doing something you care about right now. If Scalpel suspended it (reloading the page), the sound would stop abruptly, and you'd have to reload and restart playback. That ruins the experience, so Scalpel skips any tab that Chrome says is audible.

By default, this protection is on. You can turn it off in settings if you want the extension to suspend audio tabs anyway, but most people keep the default.

## How it works

When a tab plays audio, Chrome sets an audible flag on the tab object. Scalpel checks this flag during every sweep, before applying the inactivity timer. If the flag is true, the tab is not suspended, regardless of how long it's been open.

The flag is live: as soon as the page stops producing sound, Chrome clears it, and the timer starts ticking again on the next sweep. A muted-but-playing tab (audio is running, but the tab's mute button is on) is still marked audible; Chrome reports the playback state, not the user's mute choice.

## What does not matter

This doesn't protect tabs just because they once played sound; it only protects tabs actively making noise right now. Once the song ends or the call hangs up, the protection drops.

You don't need to manually protect audio tabs; the extension handles it automatically. And you can't hear the audio tab's sound from its favicon or title. If you want to know which tab is playing sound, look for the speaker icon in the tab strip.

## Code example

Here's how Scalpel checks the audible flag during a sweep:

// In the suspension worker
const tabs = await chrome.tabs.query({ windowType: 'normal' });
const protectedTabs = tabs.filter(tab => {
  if (tab.audible) {
    console.log(`Tab "${tab.title}" is playing audio, skipping`);
    return true;
  }
  return false;
});
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## How Scalpel shows it

Open Scalpel's popup and look at the settings. Under "Exclude from suspension," you'll see a toggle for "Audible tabs." When it's on (the default), any tab currently playing sound is left alone during the sweep. The stats panel also shows how many tabs are protected right now; audible tabs are part of that count.

You can test this: play music in one tab and watch the popup. The music tab won't suspend, even if your timer is set to two minutes. Stop the music, wait for the next sweep, and it becomes suspendible again.