Video Speed Controller Fox 作者： bblearning

Fork of the official add-on. Don't hesitate to install it; all the source code is available at the link—you can check it or build it yourself. The source code is also available after installing the add-on, allowing you to verify it completely.

TL;DR -- faster playback translates to better engagement and retention.

The average adult reads at 250-300 words per minute (wpm). Speech averages ~150 wpm; slide presentations often closer to 100 wpm. Given the choice, most viewers speed up playback to ~1.3-1.5x to close the gap. Accelerated viewing keeps attention longer -- faster delivery means higher engagement. With practice, many settle at 2x or above and find it uncomfortable to return to 1x.

HTML5 media elements expose a native playback rate API, but most players hide or artificially limit it. Speed adjustments should be effortless and frequent: we don't read at a fixed pace, and we shouldn't watch at one either.
Features

Universal - works on any site with HTML5 media: YouTube, Netflix, Coursera, podcasts, local files, etc.
Video and audio - controls both <video> and <audio> elements.
Fine-grained speed - 0.07x to 16x in configurable increments.
Per-site speed rules - set a default playback speed for specific domains (e.g., always 2x on lecture sites).
Per-site disable - turn off the controller on sites where you don't want it.
Remember speed - optionally persist your last speed across sessions and tabs.
Speed fightback - automatically re-applies your chosen speed when a site's player tries to reset it.
Draggable overlay - reposition the on-video speed indicator anywhere you like.
Fully customizable shortcuts - remap every key, add modifier combos (Ctrl, Shift, Alt), create multiple preferred-speed toggles.
Custom controller CSS - style or reposition the overlay with your own CSS rules.


Default keyboard shortcuts

S - decrease playback speed
D - increase playback speed
R - reset playback speed to 1.0x
Z - rewind video by 10 seconds
X - advance video by 10 seconds
G - toggle between current and preferred speed
V - show/hide the controller
M - set a marker at current position
J - jump back to the previously set marker


All shortcuts are fully customizable in the extension's settings page. You can reassign keys, add modifier combinations, and define multiple preferred-speed shortcuts with different values for quick toggling. Click Add New in settings to create additional bindings. Refresh the page after making changes for them to take effect.