How to enable YouTube Safety Mode in Your Web Browser
Safety Mode in YouTube's is currently used for parental control features. Safety Mode attempts to filter YouTube search results so that the bad stuff is hopefully weeded out. It also prevents your child from viewing material that has been flagged as inappropriate by the YouTube community or has been marked for mature audiences only by the content's creator.
Safety Mode is mainly meant to limit content of an explicit nature. YouTube makes no guarantees that it will be 100% effective at screening out the bad stuff, but at least it's a start.
To Enable YouTube Safety Mode:
1. Log in to your Google or Youtube account.
2. Go to the YouTube.com site in your web browser.
3. Click on the "Safety" button near the bottom of the YouTube homepage.
4. Click the "On" button. If you receive a message after clicking the on button that says "You can lock the Safety Mode setting after you sign in" then you are not logged into Google / YouTube. Click the "sign in" link if needed.
5. Check the box that says "Lock safety mode on this browser".
6. Click the "Save" button.
After you've clicked the save button, the page you were on will reload and you will see a banner near the top of the page that shows a check mark with the words "Successfully enabled Safety Mode" next to it.
7. IMPORTANT!! In order to prevent your child from just turning safety mode off, you must log out of your Google / YouTube account by clicking your username link in the top right-hand corner of the browser window. This will effectively lock the setting in for the browser you are using, preventing your child from disabling Safety Mode. You will need to repeat this process for all other web browsers that are on your computer (i.e. Firefox, Safari, etc).
for video tutorial you can view it here https://www.youtube.com/watch?v=u00yKwGFpS0