Describe sound and motion separately
Record whether the page starts sound, shows silent moving video or waits for a Play action. The phrase still autoplays can describe several different experiences. A noise-control preference is not necessarily a no-motion preference.
For example, a person may choose Block Audio to keep a shared workspace quiet, then later find a silent sports preview distracting. That is a changed requirement to express in the browser setting, not proof that the original sound-control rule failed.
Inspect the effective permission
Open Firefox’s Autoplay settings and compare the default with the saved permission for the actual site. Mozilla documents site exceptions that override the general choice. Use the appropriate no-motion option if that is the desired result, and save the change through the supported interface.
Return to the same page and observe an ordinary fresh start. Keep a manual click on Play separate from the page starting media on its own. If the page advances inside an already-playing session, also inspect the provider’s own next-item setting rather than assuming the browser preference controls every playback sequence.
Keep the change proportionate
Use a site-specific adjustment when only one viewing site needs a different rule. Preserve the previous preference so an experiment does not change unrelated browsing permanently. If the actual behaviour still conflicts with the recorded effective rule, collect the Firefox version, site and exact sequence.
Avoid clearing saved passwords or resetting the browser merely to compare silent motion with sound. The useful report specifies what the rule should block and what actually starts. This article explains Mozilla’s documented distinction and a focused observation method; it does not certify every website’s media behaviour.