New
- Output device per tab: "Play on" in the Booster and in every Mixer row sends a tab to other speakers or headphones. The first choice opens Firefox's device picker from a button on the page; later visits switch over with the first click on the page. Remembered per site; back to the default device if the chosen one is missing. Players in a frame of the same site follow along. Not available on Firefox for Android.
- Playback speed 0.1×–16× with a log-scale slider (Firefox plays sound between 0.125× and 8×; the popup says so outside that range).
- Speed keys on pages: S / D slower / faster, R back to 1×, G between 1× and the last speed, Z / X back / forward 10 s. Step, jump and every key can be changed or turned off, also per site. Optional: hold for 2×, A-B loop, frame steps, Shift + wheel over a video.
- A short "1.5×" badge over the video confirms a speed change (with the time left for longer videos), then disappears.
- Keyboard shortcuts for speed faster / slower / 1× (no keys by default — set them in about:addons → ⚙ → Manage Extension Shortcuts).
- Pitch: raise or lower voice and music by up to 12 semitones, independent of the speed.
- Mixer: "Same loudness in all tabs".
- Sound profiles: save all settings of a site under a name and apply them to any site in one click.
- "Only on sites I choose": every other site is left completely untouched.
- Maximum volume: 150 / 200 / 300 / 400 / 600%.
- Optional settings sync through your Firefox account.
- Exact values: click the gain or the speed to type a value; Shift + wheel over the gauge changes the gain by 1%.

Changed
- Mixer sliders set the volume of that tab only — two tabs of the same site can play at different levels.
- Equalizer: one switch per kind (Parametric, 10 bands, 31 bands); a dot shows which one is on. Presets apply to the equalizer that is on.
- Parametric EQ: a × on every band to remove it.
- A paused tab no longer keeps the computer awake (processing sleeps after 10 s without playback).
- Much lower CPU use while the popup or the sidebar is open.
- Clearer notices when a page's audio can't be processed (copy protection or audio from another site).
- Players that reset the speed when a new video starts get the site's speed again.
- The shortcut hint in Settings is now a link to Firefox's shortcut page.

Fixed
- Right after Firefox starts (restored tabs), a page could wait for its settings and speed keys went to the site.
- The limiter's "Reduction" no longer shows about −1 dB when nothing is limited.

Firefox for Android.

• Firefox for Android is supported (142 or newer)
• Fixed: on Firefox for Android the background script stopped at the missing windows / keyboard-shortcut APIs, so installing, updating and settings changes were not handled
• Mixer: mute, solo and "mute others" are hidden where the browser can't mute tabs (Firefox for Android) instead of doing nothing
• Touch: double-tap resets an EQ point or a graphic-EQ slider; EQ hints explain touch gestures; buttons and controls are at least 40 px on phones
• Phones: meters update less often and the background isn't animated, to save battery
• The popup finds the current page even when the browser opens it outside the page's window
• Minimum Firefox version is now 142 (needed for the "no data collection" declaration on all platforms; removes the AMO validation warning)