YouTube Won't Play? Download YouTube Flash Player or Try HTML5
At the very beginning, YouTube streams videos by using the Flash video format and Adobe Flash Player. From 2010, YouTube started a HTML5 opt-in trial so that you can play YouTube with HTML5 player.
So if YouTube won't play, it probably has something to do with YouTube Flash player. And the solutions depend on the platform.
YouTube Won't Play on PC
You are suggested to install the latest Adobe Flash Player by following these steps:
Method 1: Install YouTube Flash Player
1. Uninstall the older version of YouTube Flash Player and install the latest one. Download Adobe's official uninstaller here. Run the program and select your correct operating system, and then "Uninstall Flash."
2. Follow Adobe's instructions for installing the latest Flash Player for YouTube.
3. Once you've downloaded the file, quit your browser first, and then install the upgraded version of Flash player.
4. Finally, open your browser again and visit YouTube. You should now play videos successfully.
Right click on YouTube Flash player to which version is currently install on your computer.
Method 2: Try YouTube HTML5 Player
Opt in YouTube's HTML5 trial to play video with YouTube HTML5 player rather than YouTube Flash player. Adding &html5=True to the end of YouTube video URL to use YouTube HTML5 player temporarily. See 2 ways to watch YouTube without Flash.
YouTube Won't Play on Android
Some users have reported that YouTube won't play on their Samsung Android phones when try to play in HQ, while some others said YouTube won't play due to Twitter app conflict. Here here are the solutions to fix "YouTube won't play" issue.
1. If you can't play any video (not only YouTube) on the phone after some time, just remove the official Twitter app, issued by Twitter, Inc., and re-install to have a try.
2. If you guys have only YouTube videos playback problem, update the YouTube app from Android Market to the latest version.
3. For HTC Android phones, try HTC Flash Player if it exists on your Android.
YouTube Won't Play on iOS Devices like iPhone
Keep in mind that all iOS devices like iPad, iPhone, iPod don't support the Flash videos on website. The pre-installed YouTube app is the only way to watch YouTube videos on iOS devices. The YouTube app works well, but if problem happens, First, make sure your WiFi or 3G network works. Second, try to close all the apps that are currently running. Then re-open Youtube app. Reboot the devices if that doesn't take effects.
1. Hold your thumb down on an icon to get them all shaking, then close the open apps.
2. Hold home button plus power button simultaneously for a few seconds to close and restart iOS devices.