Many websites display animations using power-hungry plug-ins that can drain precious battery life, but OS X Mavericks is watching out for you. The new Safari Power Saver feature recognizes the difference between what you came to see and the stuff you probably didn’t.
If the content is front and center it plays as usual, but if it’s off in the margins, Safari Power Saver pauses it. You’ll see a static preview, and it won’t run until you click to play it. So if you don’t want to watch something, it won’t take a toll on your battery life. With Safari Power Saver, when you’re browsing websites with plug-in content, your CPU will use up to 35 percent less power.
Safari Power Saver - Click to Start Flash Plug-in
Mac OSX Mavericks and OSX Mountain lion
Safari New Versions
In the new versions of Safari (6.1 under OSX Mountain Lion, or Safari 7.0 under OSX Mavericks), there's a new feature about Power Save Settings which is enabled by default in the browser.
This feature disables all the plugin's including the Flash, which stops the videos from playing. During this phase, we would be getting some unexpected automated alerts "Safari Power Saver - Click to Start Flash Plug-in" but no error message's. Some people could think this is a bug... while it's not.
1) Go to Safari / Preferences / Advanced
2) Untick the option "Stop plug-ins to save power”