In Settings > Applications, search for Video and find Web Media Video. Tell it to preview/open in Firefox or a plugin such as VLC or Windows Media Player.

There are several ways that sites can set up webm video for viewing, including HTML5 video tags and various plugins.

Here's a test site that uses HTML5 video tags: http://www.webmfiles.org/demo-files/ (scroll down to "WebM Videos within the HTML5 <Video> Tag" where you should see a player). Does that work? If not, could you double check some settings:

(1) In a new tab, type or paste about:config in the address bar and press Enter. Click the button promising to be careful.

(2) In the search box above the list, type or paste webm and pause while the list is filtered

(3) I think you need both of these to have their default value of "true" (double-click to toggle between false and true if necessary):

• media.encoder.webm.enabled
• media.webm.enabled

Note: I'm viewing this on Windows, so there could be some differences on Mac. Please let me know if you don't find those.

Note that Firefox only plays WebM media files internally with the HTML5 media player if the video (or audio) tag is used.

You can check that via the right-click context menu in the Inspector.

• https://developer.mozilla.org/Tools/Page_Inspector

SuperSluether said

In Settings > Applications, search for Video and find Web Media Video. Tell it to preview/open in Firefox or a plugin such as VLC or Windows Media Player.

For Web Media files, I see a dropdown box with Use Opera as default, Always Ask, Save, and Use Other. I try to select Firefox under Use Other, but when I click on Open, nothing happens. Why is another browser one of the option?

cor-el said

Note that Firefox only plays WebM media files internally with the HTML5 media player if the video (or audio) tag is used. You can check that via the right-click context menu in the Inspector.

• https://developer.mozilla.org/Tools/Page_Inspector

jscher2000 said

There are several ways that sites can set up webm video for viewing, including HTML5 video tags and various plugins. Here's a test site that uses HTML5 video tags: http://www.webmfiles.org/demo-files/ (scroll down to "WebM Videos within the HTML5 <Video> Tag" where you should see a player). Does that work? If not, could you double check some settings: (1) In a new tab, type or paste about:config in the address bar and press Enter. Click the button promising to be careful. (2) In the search box above the list, type or paste webm and pause while the list is filtered (3) I think you need both of these to have their default value of "true" (double-click to toggle between false and true if necessary):

• media.encoder.webm.enabled
• media.webm.enabled

Note: I'm viewing this on Windows, so there could be some differences on Mac. Please let me know if you don't find those.

rocktivity said

cor-el said

Note that Firefox only plays WebM media files internally with the HTML5 media player if the video (or audio) tag is used. You can check that via the right-click context menu in the Inspector.

• https://developer.mozilla.org/Tools/Page_Inspector

jscher2000 said

There are several ways that sites can set up webm video for viewing, including HTML5 video tags and various plugins. Here's a test site that uses HTML5 video tags: http://www.webmfiles.org/demo-files/ (scroll down to "WebM Videos within the HTML5 <Video> Tag" where you should see a player). Does that work? If not, could you double check some settings: (1) In a new tab, type or paste about:config in the address bar and press Enter. Click the button promising to be careful. (2) In the search box above the list, type or paste webm and pause while the list is filtered (3) I think you need both of these to have their default value of "true" (double-click to toggle between false and true if necessary):

• media.encoder.webm.enabled
• media.webm.enabled

Note: I'm viewing this on Windows, so there could be some differences on Mac. Please let me know if you don't find those.

The file on the Webmfiles.org page plays, and my about:config media encoders are both on true. Exactly what should I look for in the inspector?

cor-el said

Note that Firefox only plays WebM media files internally with the HTML5 media player if the video (or audio) tag is used. You can check that via the right-click context menu in the Inspector.

• https://developer.mozilla.org/Tools/Page_Inspector

Yes, I'm using the .webm tag. Until this week, I'd just click on the URL and it would start playing.

I've downloaded a fresh version of Firefox 34.05, and under Applications, the webm video format isn't even listed.

In Preferences > Applications, you will see mostly associations that Firefox learns from outside sources. On Windows, that's initially drawn mostly the Registry; I don't know whether that information is stored on Mac. Over time as you choose different applications to handle different kinds of downloads, those will show up on that tab.

Is the website with the problem one that you manage or administer? If you can give a link to the problem page, that would be helpful.

jscher2000 said

...Is the website with the problem one that you manage or administer? If you can give a link to the problem page, that would be helpful.

I administer my sites with WordPress, which has a default HTML5 video player. But here are the pages where I've placed the URLS of WEBM videos from my server:

http://rocktivity.com/index.html

http://www.drycounty.com/jovitalk/showthread.php?p=1184280&postcount=2

http://www.democraticunderground.com/?com=view_post&forum=1002&pid=4797602

Hi rocktivity, on the first link, the server at njnation.us does not appear to be correctly configured to host .webm files. It is sending a content type of "text/plain" (first screen shot).

Similar for rocktivity.com on the second link (second screen shot).

Maybe try: https://www.google.com/search?q=apache+configure+webm

jscher2000 said

...(Your) server(s)... do...not appear to be correctly configured to host .webm files...Maybe try: https://www.google.com/search?q=apache+configure+webm

Mystery solved, and Firefox wasn't the culprit -- I didn't take into account that I changed web hosts in the past week. Updated my htaccess files as per an article at your link and it's back to normal. An excellent piece of sleuthing, sir -- I salute you!