Updated, 3/19/19, 7:30am PT: Mozilla has released Firefox 66 to the public. In addition to blocking auto-play content, the release introduces support for web authentication using Windows Hello, scroll anchoring to prevent web pages from jumping around when additional content loads, and various improvements to search. More information about Firefox 66 can be found in the release notes on Mozilla's website.
Original article, 2/5/19, 7:54am PT:
Many of us can hardly remember a time when visiting a website didn’t result in a pop-up requesting permission to send notifications, a fly-over snidely prompting us to sign up for a newsletter and at least one video that starts playing as soon as the page loads. Mozilla announced today that it wants to address one of those problems by preventing videos from automatically playing in its upcoming Firefox 66 browser.
Firefox 66 is expected to debut on March 19, and when it does, it will stop any source of audio from playing until you ask it to. Muted videos will continue to play automatically—much to the chagrin of people who don’t have the RAM to spare.
There are some exceptions. The most important one is for sites that Firefox users “whitelist” themselves.
“There are some sites on which users want audible autoplay audio and video to be allowed. When Firefox for Desktop blocks autoplay audio or video, an icon appears in the URL bar. Users can click on the icon to access the site information panel, where they can change the ‘Autoplay sound’ permission for that site from the default setting of ‘Block’ to ‘Allow’. Firefox will then allow that site to autoplay audibly. This allows users to easily curate their own whitelist of sites that they trust to autoplay audibly," Mozilla explained.
Firefox 66 will also let sites that people have allowed to access their camera or microphone to automatically play audible content. This is supposed to ensure “that sites which have explicit user permission to run WebRTC should continue to work as they do today.”
The initial version of this tool will only block audio played via HTMLMediaElement. Audio served via the Web Audio API won’t be blocked via the initial version of this tool because Mozilla hasn’t finalized its implementation for that feature. However, Mozilla said “we expect to ship with autoplay Web Audio content blocking enabled by default sometime in 2019.” Until that happens, Firefox 66 will only block a portion of the annoying noises emanating from web pages, (and yes, we understand that Tom’s Hardware is throwing a stone inside a glass house).