Tired of an Overcrowded Watch Later List? Here’s How to Declutter and Enjoy Your Videos!

1. On your YouTube ‘Watch Later’ page…
2. Right-click anywhere on the page and click on “Inspect”.
3. In the DevTools window that appears, click on the Console tab.
4. Copy and paste the following code into the Console:

setInterval(function () {
    video = document.getElementsByTagName('ytd-playlist-video-renderer')[0];

    video.querySelector('#primary button[aria-label="Action menu"]').click();

    var things = document.evaluate(
        '//span[contains(text(),"Remove from")]',
        document,
        null,
        XPathResult.ORDERED_NODE_SNAPSHOT_TYPE,
        null
    );

    for (var i = 0; i < things.snapshotLength; i++) 
    {
        things.snapshotItem(i).click();
    }
}, 500);

from this GitHub repo