TestTube lets you join experiments on YouTube

Martin Brinkmann
May 6, 2015
Music and Video

TestTube is a new experimental page on YouTube that lists some of the experimental new features that Google is currently testing on the site.

Google likes to test new features in so-called labs before it decides whether to make them available to all users on a site.

The first Google service to introduce a labs feature was Gmail and it is available up to this point in time. There you find options to add new functionality to Gmail, for instance a Google Calendar widget or a quick links widget to open Gmail pages quickly.

TestTube works similar to that. You visit the page which displays publicly available experimental features that you can enable or try out on the site.

For now, there are only two features listed on the page of which one seems to be available to all users on the site provided they have the hardware to make use of it.

The first feature listed is 4K video in 60 frames per second. The page lists a playlist of 4K videos to watch on YouTube and suggests to find other videos available in 4K by using the filter on YouTube to display only 4K videos in the results.

To do that, simply search for something on YouTube, click on the filters button at the top left afterwards and then on 4K under features.

youtube 4k

4K videos play out of the box in Google Chrome. If you are using Firefox, you may need to make changes to the browser's configuration before the option becomes available in the browser.

  1. Type about:config in the browser's address bar and hit enter.
  2. Confirm that you will be careful if the prompt appears.
  3. Search for the following parameters and make sure their values are set correctly:
  4. media.fragmented-mp4.exposed is set to true.
  5. media.fragmented-mp4.ffmpeg.enabled is set to true.
  6. media.mediasource.enabled is set to true.

firefox youtube 4k

Restart the web browser afterwards and you should get the 4K options in the video quality menu provided that the video itself has been recorded in that resolution.

youtube 4k firefox

The second experiment enables a new player interface on YouTube. It is highlighted in the screenshot above and the two core differences to the current player are the player's transparency and the fact that it hides after a moment automatically.

You can enable the new player and restore the original player at any time on the same page if you want to return to it.

This is easier than having to modify a cookie on YouTube to enable the new player on the site.

Two experiments may not look like much but if you think back to how Gmail Labs started, you will realize that it started with just a couple of experiments as well and that the list grew gradually over time.

TestTube lets you join experiments on YouTube
Article Name
TestTube lets you join experiments on YouTube
TestTube lets you join experimental features on YouTube that Google wants to test before deciding whether to make them available for all users on the site.

Tutorials & Tips

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  1. Anonymous said on August 1, 2010 at 12:43 pm

    Why not make use of the mplayer.conf?

  2. Mike J said on August 1, 2010 at 2:58 pm

    Huh, I have never even seen this “font cache” pane; videos play at once for me, using VLC & XP SP3.

    1. Martin said on August 1, 2010 at 3:39 pm

      Mike, in theory this should have only been displayed once to you, at the very first video that you played with VLC. The time this window is displayed depends largely on the number of fonts in your font directory.

      1. Mike J said on August 2, 2010 at 2:30 pm

        huh, I lucked out for a change?? Amazing!!
        Apparently VLC keeps this info through version updates, but I didn’t see this message after a fresh OS install about 8 weeks ago, & a new VLC.

  3. myo said on August 1, 2010 at 5:52 pm

    yes, yes, i have the same problem. sometimes, VLC crashes when it is playing .mov file.

  4. Kishore said on August 13, 2010 at 2:55 pm

    Buidling font Cache pop-up


    Open VLC player.

    On Menu Bar:


    (at bottom – left side)
    Show settings — ALL

    Open: Video
    Click: Subtitles/OSD (This is now highlited, not opened)
    Text rendering module – change this to “Dummy font renderer function”


    Re-open – done.
    Progam will no longer look outside self for fonts

    Source – WorthyTricks.co.cc

    1. Martin said on August 13, 2010 at 3:10 pm

      Great tip, thanks a lot Kishore.

  5. javier said on August 14, 2010 at 1:50 pm

    @Kishore, I’ll try your tips, but does this mean it will no longer show subtitles either?
    I do use subtitles, but the fontcache dialog box pops up (almost) everytime I play a file.

    Could this be related to the fonts I have installed? Or if I add/remove fonts to my system?

    I’ll try to do a fresh install also, if your tips does no work. I’ll post back here later…


  6. Kishore said on August 15, 2010 at 12:38 pm

    @ Javier, The trick i posted will show up subtitles too. If not,

  7. Kishore said on August 15, 2010 at 12:39 pm

    @ Javier, The trick i posted will show up subtitles too. If not,Dont worry, VLC is currently sorting out this issue and the next version will be out soon.

    No probs @ Martin !! Its my pleasure

  8. Ted said on October 22, 2010 at 3:57 am

    Try running LC with administrator privileges. That seemed to fix it for me

  9. Evan said on December 8, 2013 at 1:48 am

    I am using SMplayer 0.8.6 (64-bit) (Portable Edition) on Windows 7 x64. Even with the -nofontconfig parameter in place SMplayer still scans the fonts. Also, I have enabled normal subtitles and it is still scanning fonts before playing a video. Also, it does this every time the player opens a video after a system restart (only the fist video played).

  10. Mike Williams said on September 6, 2023 at 1:26 pm

    Does that mean that only instrumental versions of songs will be available for non-paying users?

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