Sometimes, the video or audio content in a web page cannot be properly downloaded and displayed in Firefox. This article will help you solve these problems.

Note: If you're having trouble with a website, click the padlock icon in the address bar to see if Firefox has blocked insecure parts of the page. See Mixed content blocking in Firefox for details.

HTML5 audio and video

Firefox has built in support for open media formats usually associated with WebM, Ogg and Wave containers. However MP3 and MP4 containers usually depend on platform decoders for MP3, AAC and H.264 audio and video streams. For more information, see Fix video and audio problems on Firefox for Windows N editions and HTML5 audio and video in Firefox.

Clear the cache

See How to clear the Firefox cache.

Disable interfering extensions or ad-blocking software

Ad-blocking software, such as anti-banner filters of your Internet Security program, or extensions, such as Flashblock or Adblock Plus, can prevent audio or video content from playing.

• If the site works with ad-blocking disabled, you may want to add the site to your whitelist in your adblocker filter.
• If the video or audio plays when you disable all extensions, then one of your extensions was causing the problem. For more information, see Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems.

Check some Firefox settings

• Cookies:

1. In the Menu bar at the top of the screen, click Firefox and then select Preferences or Settings, depending on your macOS version.Click the menu button and select Settings.
2. Select the Privacy & Security panel and go to the Cookies and Site Data section.
3. Verify that cookies are enabled and that the site is not blocked in the Exceptions list.

• History:

1. In the Menu bar at the top of the screen, click Firefox and then select Preferences or Settings, depending on your macOS version.Click the menu button and select Settings.
2. Select the Privacy & Security panel and go to the History section.
3. Make sure that Firefox is set to Remember history.

• Pop-up windows:

1. In the Menu bar at the top of the screen, click Firefox and then select Preferences or Settings, depending on your macOS version.Click the menu button and select Settings.
2. Select the Privacy & Security panel and go to the Permissions section.
3. Allow the website as an exception to the "Block pop-up windows" setting.

Flash Plugin

The Flash plugin is used for embedded audio and video on some websites. When the Flash plugin is missing, a message will appear in place of the content:

• "A plugin is needed to display this content" indicates that the plugin is not installed on your machine.

  

See Install the Flash plugin to view videos, animations and games and Flash Plugin - Keep it up to date and troubleshoot problems.

Note: If Flash is disabled in the Add-ons Manager, you won't be able to use it.

1. Click the menu button , click Add-ons and themes and select Plugins.
2. Review the list of plugins.
   • To enable Flash, click on Never Activate and select Ask to Activate in its drop-down menu.

If you see an Activate Flash icon on web pages, where the plugin content should be, you'll need to click on the icon to activate the plugin:

For more information, see Why do I have to click to activate plugins?.

Allow Plugin Container in your Internet security program

Allow your Internet security software (including firewalls, antivirus programs, anti-spyware programs, and more) to trust Plugin Container for Firefox. For detailed instructions, see Configure firewalls so that Firefox can access the Internet where in that case Firefox means Plugin Container for Firefox.

Reset preferences

See Reset Firefox preferences to troubleshoot and fix problems.

Remove specific entries in the hosts file (advanced users)

If you use a hosts file, you can temporarily disable it by renaming it Xhosts. Or, you can edit the hosts file to remove specific entries such as ad.doubleclick.net that can cause videos on certain sites to fail (for more information, see this MozillaZine forum thread). To apply changes to your hosts file, you may need to flush the DNS cache by entering the command: ipconfig /flushdns in the Run dialog box on Windows.

Based on information from Video or audio does not play (mozillaZine KB)