diff --git a/app/assets/prefs.js b/app/assets/prefs.js
index fc539760e7..0541de545e 100644
--- a/app/assets/prefs.js
+++ b/app/assets/prefs.js
@@ -141,3 +141,15 @@ pref("mousewheel.with_alt.action", 1);
 
 // Use the system print dialog instead of the new tab-based print dialog in Firefox
 pref("print.prefer_system_dialog", true);
+
+// Disable libvpx decoding/encoding
+pref("media.webm.enabled", false);
+pref("media.encoder.webm.enabled", false);
+pref("media.mediasource.webm.enabled", false);
+pref("media.mediasource.webm.audio.enabled", false);
+pref("media.mediasource.vp9.enabled", false);
+pref("media.ffvpx.enabled", false);
+pref("media.ffvpx.mp3.enabled", false);
+pref("media.rdd-vpx.enabled", false);
+pref("media.rdd-ffvpx.enabled", false);
+pref("media.utility-ffvpx.enabled", false);