Volume Booster

1. Download the zip above and unzip it. You get a folder called mes-volume-booster. Keep it somewhere permanent (Documents is fine): the browser reads the extension from that folder.
2. Open the extensions page: chrome://extensions in Chrome, brave://extensions in Brave, edge://extensions in Edge.
3. Turn on Developer mode (a switch at the top right, or on the left in Edge).
4. Click Load unpacked and choose the unzipped mes-volume-booster folder.
5. Click the puzzle-piece icon in the toolbar and pin MES Volume Booster.

Chrome may show a "disable developer mode extensions" notice when it starts: choose Cancel / Keep. Brave and Edge usually do not. Until the extension is listed in the Chrome Web Store, updates are manual: download the new zip, replace the folder and press the reload arrow on the extensions page. Firefox is not supported yet.

• Open the page with the quiet video, start it, click the toolbar icon and drag the slider or tap a preset (150%, 200%, 300%, 400%, 600%). The icon shows the level as a badge.
• Two modes (the switch at the top of the popup): Video (the default) boosts the video player on the page, which covers YouTube and most video sites, with no recording dot. Whole tab boosts all the sound of the tab: use it for a video that sits inside another site's frame, for audio-only pages or when Video mode says it cannot boost a video.
• Alt+Shift+Up / Down make the current tab louder / quieter without opening the popup. Change the shortcuts at chrome://extensions/shortcuts.
• Set the slider back to 100% to return to normal. In Whole tab mode there is also a button to turn the boost off and release the tab.
• Settings: the default mode, the highest boost (200%, 400% or 600%), the shortcut step, the soft limiter, and whether it remembers each site's last level.

• Protect your ears and speakers. A boost of 300% is about +9.5 dB and 600% about +15.6 dB. Start low and go up slowly, especially with headphones. The popup shows the boost in decibels.
• The site's own volume still works. The boost multiplies whatever the video's volume slider is set to, so for the most headroom keep the site's slider at its top.
• Why Whole tab mode shows a recording dot. To make a whole tab louder the extension receives that tab's sound from the browser (its tab-capture feature), changes the volume and plays it back, and Chrome marks such a tab with a small indicator. Nothing is recorded or sent anywhere. Video mode does not need this and shows no dot.
• The soft limiter rounds off the loud peaks that a big boost creates instead of letting them clip. Quiet sound is boosted by exactly the percentage shown. Turn it off for the raw boost.
• Limits. It cannot boost browser pages (chrome://) or the Web Store. Video mode only touches videos that the page itself serves (the normal case for YouTube and other streaming sites); a video file loaded from another site that does not allow it cannot be routed safely, and the popup then suggests Whole tab mode. If the page has not been clicked yet the browser keeps its audio engine paused: click the page once and move the slider again. Whole tab mode needs Chrome 116 or newer and does not work on a tab that another extension is already capturing. Boosting is per tab: other tabs stay as they are.

activeTab and scripting let the extension add the booster to the page you are on, only when you click the icon or press the shortcut (Video mode); tabCapture and offscreen are used only in Whole tab mode to receive the tab's sound and process it in a hidden page; storage keeps your settings and remembered levels. It does not ask to read your data on all websites and never reads page content.