playing video without flash player

There is no alternative to Adobe Flash Player for viewing Flash content on a web page. The Safari extensions "ClickToFlash" and "ClickToPlugin" prevent Flash content from loading automatically, and will also cause non-Flash video to be substituted for Flash on YouTube and maybe some other sites. Similar extensions must exist for Firefox and Chrome, but I'm not familiar with them. You must always do your own research to determine the safety and effectiveness of any third-party software before using it.

To watch videos at youtube.com use HTML5 viewer

https://www.youtube.com/html5

Did you go to the link that I provided in my previous reply?

Light-blue text is a link

HTML5 is the fifth version of Hyper Text Marup Language.

https://en.wikipedia.org/wiki/HTML5

Your web browser interprets the "language" of the website and display what the website want you to see. Thus, it is built into the browser, not a sepeare app.

The link I gave you was for youtube.com only. Thus, not applicable to other websites.

Silver Light is Microsoft's media play/interface that is similar in use as Flash. Microsoft stopped development Of Silver Light years ago:

Microsoft announced the end of life of Silverlight 5 in 2012. In 2013, Microsoft announced that they had ceased development of Silverlight except for patches and bugfixes. Silverlight is no longer supported in Chrome on OS X, while support for Silverlight in Chrome on all other operating systems was disabled by default in April 2015 and will be removed completely in September 2015.^[5]Microsoft has set the support end date for Silverlight 5 to be October 2021.^[6] In 2015, Microsoft announced that since support for ActiveX will be discontinued with Microsoft Edge, Silverlight will not be supported in that browser.^[7]

https://en.wikipedia.org/wiki/Microsoft_Silverlight