Is Flash Player safe to use on Mac's?

Flash is fine to use. Get it only from the official Flash site. Do not download Flash from other sites. When using Chrome you are using Flash. It is built into Chrome.

for casual user its almost safe to use flash, just not forget to update it

Flash is buggy. It has lots of holes in it, like Swiss cheese. Hackers are constantly finding new ways to exploit it, so you need to be sure to keep it up-to-date. Adobe tries to keep up by updating it frequently. Download it ONLY from here:

https://get.adobe.com/flashplayer/

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Unexpected Flash on Web pages drives me crazy. So I have installed "Click-to-Plugin" the evolved replacement of "Click-to-Flash".

http://hoyois.github.io/safariextensions/clicktoplugin/

When Flash windows are encountered, they are replaced with or overlaid with an oval with ( Flash ) showing. IF you want to play, you click the oval, otherwise it does not spend system resources playing junk you do not care about..

Flash is in well-deserved decline, but Flash content is still widespread on the Web. Although Flash vulnerabilities are often found by security researchers, I know of no active exploits against it on OS X at the moment.

There is no alternative to Adobe Flash Player for viewing Flash content. If you choose to install it, you can reduce your exposure by checking the box marked

Stop plug-ins to save power

in Advanced tab of the Safari preferences window, if it's not already checked.

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.