The ads you see while watching YouTube videos are tailored to your interests and based on your Google Ad Settings, the videos you’ve viewed, and whether you're signed in or not.

When you're logged in, these anonymous signals may determine which ads you see:

• Types of videos you’ve viewed
• The apps on your device and your use of apps
• Websites you visit
• Anonymous identifiers associated with your mobile device
• Previous interactions with Google’s ads or advertising services
• Your geographic location
• Age range
• Gender
• YouTube video interactions

Whether you are signed in or not, the ads you see are based on the content of the videos you’ve viewed.  

Manage privacy settings for ads

You can control the ads that are delivered to you based on your Google Account across devices in your Ad Settings. You can also view, delete, or pause your YouTube watch history.

* Nguồn: Youtube