User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:56.0) Gecko/20100101 Firefox/56.0 Build ID: 20170624030209 Steps to reproduce: Go to http://wolnosc24.pl/2017/06/24/to-nagranie-poszlo-juz-w-swiat-kibice-jasno-dali-do-zrozumienia-co-sadza-o-tzw-uchodzcach-cala-polska-spiewa-z-nami-wideo/ Actual results: In attachment you can see comparison between Chrome and Nightly - Facebook video is not displayed in Nightly

WFM in Mozilla/5.0 (Windows NT 10.0; WOW64; rv:56.0) Gecko/20100101 Firefox/56.0 (20170624030209).

Somehow for me it doesn't.

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:56.0) Gecko/20100101 Firefox/56.0 Build ID: 20170627113424 Hi and thanks for the report! I tried to reproduce the issue you described in comment 0 but without success. The videos from the link you provided are displayed on all Firefox channels (Nightly, Beta and release) using Windows 10 x64. Does this happen only on Nightly channel on your side? Release and Beta channels are displaying the videos properly? Also, can you please retest this using a new clean Firefox profile, maybe even safe mode, to eliminate custom settings as a possible cause (https://goo.gl/AR5o9d)? Thanks!

On all releases in new profiles there was no problem. On old profile still no video visible. I have ublock origin and two others add-ons, but nothing changed when I disabled them.

Take a look at about:support to see if there is any obvious profile cruft in the modified preferences list. Failing that attach about:support to the bug.

When I clicked Restart with Addons disabled and then Enter Safe Mode, video was displayed. When I restarted with add-ons enable and I disabled them one after another, video wasn't displayed every time. This is about:support Troubleshooting Information This page contains technical information that might be useful when you're trying to solve a problem. If you are looking for answers to common questions about Nightly, check out our support web site. Application Basics Name Firefox Version 56.0a1 Build ID 20170710030203 Update History Update Channel nightly User Agent Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:56.0) Gecko/20100101 Firefox/56.0 OS Windows_NT 10.0 Profile Folder Enabled Plugins about:plugins Build Configuration about:buildconfig Memory Use about:memory Performance about:performance Registered Service Workers about:serviceworkers Multiprocess Windows 1/1 (Enabled by user) Stylo false (disabled by default) Google Key Found Mozilla Location Service Key Found Safe Mode false Profiles about:profiles Crash Reports for the Last 3 Days Report ID Submitted All Crash Reports Nightly Features Name Version ID Activity Stream 0.0.0 activity-stream@mozilla.org Application Update Service Helper 2.0 aushelper@mozilla.org Click-to-Play staged rollout 1.2 clicktoplay-rollout@mozilla.org Firefox Screenshots 10.3.0 screenshots@mozilla.org FlyWeb 1.0.0 flyweb@mozilla.org Follow-on Search Telemetry 0.9.1 followonsearch@mozilla.com Form Autofill 1.0 formautofill@mozilla.org Multi-process staged rollout 1.70 e10srollout@mozilla.org Photon onboarding 0.1 onboarding@mozilla.org Pocket 1.0.5 firefox@getpocket.com Presentation 1.0.0 presentation@mozilla.org Shield Recipe Client 55 shield-recipe-client@mozilla.org Web Compat 1.1 webcompat@mozilla.org WebCompat Reporter 1.0.0 webcompat-reporter@mozilla.org Extensions Name Version Enabled ID Avast Online Security 12.0.222 true wrc@avast.com Enhancer for YouTube™ 2.0.17 true enhancerforyoutube@maximerf.addons.mozilla.org uBlock Origin 1.13.4 true uBlock0@raymondhill.net Avast SafePrice 12.0.222 false sp@avast.com Graphics Features Compositing Direct3D 11 Asynchronous Pan/Zoom wheel input enabled; scrollbar drag enabled WebGL 1 Driver WSI Info EGL_VENDOR: Google Inc. 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The video shows if you disable Tracking Protection.

François - we appear to be blocking Facebook embeds and it is making Firefox seem broken. Is there a way we can improve the user experience here?

The Facebook domains are on the Disconnect list: https://github.com/mozilla-services/shavar-prod-lists/blob/218c5dffa23b72d23520c9926219b3ac34225ed7/disconnect-blacklist.json#L6-L16 These are the Facebook blocked resources from the devtools console: > The resource at “http://connect.facebook.net/pl_PL/sdk.js#xfbml=1&version=v2.0” was blocked because tracking protection is enabled. > Loading failed for the <script> with source “http://connect.facebook.net/pl_PL/sdk.js#xfbml=1&version=v2.0”. > The resource at “https://www.facebook.com/plugins/video.php?href=https%3A%2F%2Fwww.facebook.com%2FStadionowiOprawcy.net%2Fvideos%2F1366852993398561%2F&show_text=0&width=560” was blocked because tracking protection is enabled.

The video itself is contained within an iframe: <iframe style="border: medium none; overflow: hidden; max-width: 100%;" src="https://www.facebook.com/plugins/video.php?href=https%3A%2F%2Fwww.facebook.com%2FStadionowiOprawcy.net%2Fvideos%2F1366852993398561%2F&amp;show_text=0&amp;width=560" scrolling="no" allowfullscreen="allowfullscreen" width="560" height="309" frameborder="0"></iframe>