See Video Documentation :- 

Before - When video tag Download is Enabled .

Here is a Simple Video Tag :-

 

    <video width\="320" height\="240" controls loop\>

        <source src\="https://www.w3schools.com/tags/movie.mp4" type\="video/mp4"\>

        Your browser does not support the video tag.

    </video\>

-- Preview --

Your browser does not support the video tag.

For Disabling the Download Option 

After Disabling Download

Add This Attribute 

controlslist\="nodownload"

Now the Full Code Will Look Like :-

 

    <video width\="320" height\="240" controls loop controlslist\="nodownload"\>

        <source src\="https://www.w3schools.com/tags/movie.mp4" type\="video/mp4"\>

        Your browser does not support the video tag.

    </video\>

-- Preview --

Your browser does not support the video tag.

Possible controlslist Values :- 

• nofullscreen
• nodownload
• noremoteplayback

Download Files Used in This Video :-  https://github.com/CXDI/youtube-files/blob/main/Tips/Disable_Download_option_in_HTML5_Video.html