Fix NS_E_FLASH_PLAYBACK_NOT_ALLOWED (0XC00D10CF) in Windows Media Player

You open a video file or stream in Windows Media Player (WMP) and get hit with a pop-up saying "NS_E_FLASH_PLAYBACK_NOT_ALLOWED" and the code 0XC00D10CF. Usually this happens when you try to play a file that uses Flash—like an older .swf animation, a Flash-based video from a local folder, or a web link that still uses Flash. I see this most often on Windows 10 and Windows 11 systems where Flash Player is installed but WMP blocks it by default.

I know this error is infuriating—you click play, and nothing happens. Just a wall of text. The root cause is simple: Microsoft disabled Flash playback in Windows Media Player for security reasons. Internet Explorer also blocked Flash years ago. But if you still need to run old Flash content locally, WMP has a hidden setting that stops it from loading Flash content.

Here's the fix. It's quick—takes about 2 minutes.

How to Enable Flash Playback in Windows Media Player

1. Open Windows Media Player. You can search for it in the Start menu.
2. Press Alt + T on your keyboard to open the Tools menu. If nothing happens, click the Organize button in the top-left, then choose Options.
3. Click the Player tab.
4. Look for a checkbox that says "Turn on Flash playback". It's near the bottom of the window. Check it.
5. Click OK to save.
6. Close and reopen Windows Media Player. Try playing your file again.

That should fix the error. The reason this works is because WMP has a built-in block for Flash content—this checkbox toggles that block off.

If You Don't See the Checkbox

Some versions of Windows 10 and Windows 11 removed the checkbox entirely. If it isn't there, you've got another way to fix this:

1. Press Windows + R, type regedit, and hit Enter.
2. Go to this key (copy and paste it):
   HKEY_CURRENT_USER\Software\Microsoft\MediaPlayer\Player
3. Right-click on the right side, choose New > DWORD (32-bit) Value.
4. Name it FlashPlaybackEnabled.
5. Double-click it and set the value to 1.
6. Close Registry Editor. Restart WMP.

If that registry key doesn't exist, create the Player folder (key) under MediaPlayer if needed. This trick worked on Windows 10 version 22H2 for me.

Still Getting the Error?

Two more things to check:

• Is Flash Player actually installed? If you uninstalled Flash years ago, WMP can't play Flash files at all. Adobe stopped supporting Flash in 2021, but some third-party players like VLC still handle it. You can check in Control Panel > Programs and Features for "Shockwave Flash Object" or similar.
• Try a different player. Honestly, Windows Media Player is old and cranky with Flash. Download VLC Media Player (free) or Media Player Classic - Home Cinema. Both play Flash files without the block. I switched to VLC myself when this error kept popping up.

One last thing: if you're trying to open a Flash file from a website, the browser itself may block it. That's a different problem. The fix here is for local files only.

Hope this gets you back to playing those old animations or videos. I've helped a dozen people with this exact code—the registry trick usually does it when the checkbox is missing.