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Go to https://www.youtube.com/ in your browser. This will open your YouTube home page if you're logged into your YouTube account. If you aren't logged into your YouTube account, click SIGN IN in the top-right corner of the page, then enter your email address and password. It's in the top-right corner of the YouTube page. Clicking it prompts a drop-down menu. You'll find this option in the drop-down menu. Doing so opens the Settings page. If you use the old version of YouTube, you'll instead click the gear-shaped icon {"smallUrl":"https:\/\/www.wikihow.com\/images\/3\/30\/IE11settings.png","bigUrl":"\/images\/thumb\/3\/30\/IE11settings.png\/30px-IE11settings.png","smallWidth":460,"smallHeight":460,"bigWidth":"30","bigHeight":"30","licensing":"<div class=\"mw-parser-output\"><p>I edited this screenshot of a Windows icon.\n<\/p><p>License: <a rel=\"nofollow\" class=\"external text\" href=\"http:\/\/en.wikipedia.org\/wiki\/Public_domain\">Public Domain<\/a><br>\n<\/p><\/div>"} in the drop-down menu. It's at the bottom of the page. This will open an additional section of options below the bottom of your browser window. This is at the bottom of the page. It's at the very bottom of the page, below the "Restricted Mode" section. Doing so will save your changes and disable Restricted Mode for your account. Close the YouTube tab, then open a new tab and go back to YouTube. This will reset YouTube's cache, allowing previously restricted videos to show up in your subsequent searches.

Summary:
Open YouTube. Click your profile icon. Click Settings. Click the "Restricted Mode" drop-down box. Scroll down and check the "Off" box. Click Save. Close and re-open YouTube.