Does the same thing as "javascript:(function(){ var nsfw_url = window.location.href ;var isyt = nsfw_url.indexOf("youtube.com");if (isyt != -1 && nsfw_url.indexOf("nsfwyoutube.com") == -1){ var final = nsfw_url.replace("youtube.com", "nsfwyoutube.com"); window.location = final; } else {alert ("You have to be on youtube.com for this to work!");} })();"