Optimize and address Flash performance in OS X

Adjusting some Flash and system settings may help when Flash Web content hangs or shows choppy performance.

Topher Kessler MacFixIt Editor
Topher, an avid Mac user for the past 15 years, has been a contributing author to MacFixIt since the spring of 2008. One of his passions is troubleshooting Mac problems and making the best use of Macs and Apple hardware at home and in the workplace.
Topher Kessler
3 min read

Adobe's Flash player provides access to a great deal of online content, including that from popular sites like YouTube; however, there may be times when visiting sites that use the plug-in results in choppy performance or an inability to connect to the media being presented, which may happen on all installed and updated Web browsers. If this happens on your system, you have several options to optimize the plug-in's performance and get the sites working again.

  1. Update Flash
    First if you are having troubles with Flash, then be sure to fully update to the latest version. This will not only increase the security of Flash, but also implement bug fixes that may help the management of certain Flash content. You can get the latest version of Flash from the Adobe Flash download page.
  2. Flash player settings
    In the settings for Flash you can enable or disable hardware acceleration here (click for larger view). Screenshot by Topher Kessler/CNET
  3. Toggle hardware acceleration
    The latest versions of Flash include options for using GPU power to render Flash content and thereby prevent CPU spikes. This option is available by right-clicking the Flash content and choosing Settings. In the window that appears, click the first tab (that looks like a small screen) and check or uncheck the "Enable hardware acceleration" option to see if this changes anything.
  4. Turn off Flash management plug-ins
    Often people install plug-in managers like Click to Flash, which will block all Flash content unless you explicitly activate it. These and other plug-ins may interfere with Flash's performance, so try disabling or uninstalling them to see if that helps your problem.
  5. Disable extensions
    In addition to browser plug-ins, Safari and other browsers support individual extensions that may offer similar Flash-blocking options, so try disabling extensions for your browser to see if this helps. In Safari this can be done in the Extensions section of the preferences, and in Firefox you can choose Add-Ons from the Tools menu to get to the plug-ins and extensions manager.
  6. Flash Player system preferences
    Clicking this button in the Flash Player system preferences will clear all saved data and settings from sites that use Flash (click for larger view). Screenshot by Topher Kessler/CNET
  7. Change local storage settings for Flash
    Another optimization trick for Flash is to adjust the local storage settings, which, like a cache, may help smooth media playback, especially on slower or less stable connections. To do this you can again right-click the Flash content and go to the settings, and this time choose the third tab and increase the storage amount for the current media server.
  8. Clear all local storage for Flash
    Akin to clearing system caches or browser caches to boost performance, you can also do the same for the Flash plug-in itself by deleting all previously stored files and settings for Flash content. To do this, go to the Flash Player system preferences, and in the Storage section click the Delete All... button. This will only remove stored content, so another similar approach is to remove this and any settings associated with Flash, which can be done by clicking the Delete All... button in the Advanced section of the preferences.
  9. OS X MTU settings
    In your network connection's Advanced settings, slightly lower the MTU size in the hardware section to see if that helps dropped connections (click for larger view). Screenshot by Topher Kessler/CNET
  10. Adjust system's network MTU size
    The MTU or Maximum Transmission Unit in a network connection is the largest size of the data portion of a network packet. Each packet contains header information (where the data is coming from and going to), and then the data itself. While setting the system to use larger MTUs will usually lead to fewer packets needing to be sent and therefore reducing network overhead, if the packets are too large for the network services being used, then the network connection may begin dropping them. Even though the standard Ethernet MTU size of 1,500 bytes should work in most cases and should offer optimized network speeds, it may be too large for some negotiated connections and result in dropped packets. Therefore, dropping the size slightly may prevent packet loss while only minimally cutting into network performance, and thereby increasing the overall connection stability.

    To change the MTU size in OS X, go to the Network system preferences and choose your active connection. Then click the Advanced button and go to the Hardware tab. In here, select Manually from the Configure menu, and then select Custom from the MTU menu. When you do this, the entry field below the two menus will become active, and you can try lowering the MTU value. It is generally best to keep the value above 1,400 bytes, but you can try several different common values, including 1,472 and 1,453, which seem to work best for networks with problematic connections.

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