As of December 2014, YouTube now requires you to have 500 Subscribers before becoming eligible for a custom channel URL. YouTube recently has changed how new accounts make custom URL's for a channel. You can find the requirements and instructions below on how to now change a username on a new channel. Eligibility requirements To get a custom URL for your channel, your account needs to be in good standing and meet a few other requirements: 500 or more subscribers Channels is at least 30 days old Channel has uploaded a photo for the channel icon Channel has uploaded channel art You can also qualify for a custom URL by linking and verifying your official webpage with your channel or +Page. Get a Custom URL for your channel Once you've qualified for a custom URL, you'll receive an email notification and a notification on your Creator Studio dashboard. To get your custom URL: Sign in to YouTube and navigate to the Creator Studio. Look for your Get a new custom URL notification and click in the included link You'll be redirected to claim a custom URL. You'll see the custom URL(s) you've been approved for. These cannot be changed. You may also need to add a few letters or numbers to make the URL unique to you. Click the box next to I agree to the Terms of Service then click Change URL in the bottom left corner. This URL will be linked to both your YouTube channel and your Google+ identity. Once your URL has been approved, you cannot request to change it. When you're certain, click Confirm choice.